My favourites are 39D for the clever clue construction and 48D for the definition.
ACROSS
1 Opener in Irish county’s team (9)
CORKSCREW – CORKS = Irish county’s, CREW = team
6 Marvellous evening meal down by a piano (5)
SUPER – SUP{p}ER = evening meal
9 Gullible person said to require assistance when distressed (7)
SUCCOUR – sounds like SUCKER = gullible person
13 Confines or rather restricts maiden (5)
AMBIT – A BIT = rather, around M = maiden
14 Leave military formation in radioactive dust cloud (4,3)
FALL OUT – double definition, the second referring to FALLOUT
15 Revolutionary princess rises up behind (2,7)
IN ARREARS – INAR = RANI = princess, reversed, REARS = rises up
16 Vanishing cream consumer? (8,3)
CHESHIRE CAT – cryptic definition. Presumably cream consumer as the cat that got the cream is supposed to be happy, therefore smiling
17 Untimely error a Cornishman corrected (11)
ANACHRONISM – (A CORNISHMAN)*
18 Savage to devour rook and chicken portion (6)
BREAST – BEAST = savage, around R = rook
19 Hard material found in two clubs (8)
IRONWOOD – IRON, WOOD both (golf) clubs
21 Tablet provided with article about fabulous bird (6)
TROCHE – THE = article, around ROC = fabulous bird. Just needed to check which type of tablet this meant for my own edification
25 One mistakenly printed in bold (8)
INTREPID – (PRINTED IN)*
26 Faintest star is this to my knowledge (2,3,2,1,3,3)
AS FAR AS I CAN SEE – double definition
28 Fat politician consumed by booze (5)
AMPLE – ALE = booze, around M.P. = politician
29 Hard work associated with an identifying phrase (6)
SLOGAN – SLOG = hard work, AN
30 Inside spread little money about congregation (10)
CENTREFOLD – CENT = little money, RE = about, FOLD = congregation
33 Noblewoman about ready to reform Republican fantasist (10)
DAYDREAMER – DAME = noblewoman, around READY*, R = Republican
35 Heard musical bouzouki-playing here? (6)
GREECE – sounds like GREASE = musical
36 Oriental verse reporting shrill sound made by dove? (5)
HAIKU – sounds like HIGH = shrill, COO = sound made by dove
38 Serious measure to change unpopular work period (9,5)
GRAVEYARD SHIFT – GRAVE = serious, YARD = measure, SHIFT = change
40 Maybe oil one found in desert to harbour’s east (8)
PORTRAIT – PORT = harbour, RAT = desert, around I = one
42 Scottish fellow coming in shaved bald nut (6)
ALMOND – {b}ALD around MON = Scottish fellow
43 What might get me in post corruptly? (8)
NEPOTISM – (ME IN POST)*
44 Right to support the monarch (6)
PROPER – PROP = support, E.R. = the monarch
47 Chimpanzee, missing first note, so plays fiddle (5,6)
PONZI SCHEME – (CHIMP{a}NZEE, SO)*
50 Say Ransome’s behind bit of capital raised (7,4)
ARTHURS SEAT – ARTHURS = Ransome’s, SEAT = behind
52 Tedious don is with Greek poet wasting hour (9)
WEARISOME – WEAR = don, IS, {h}OME{r}
53 Fruit when cut keeps good colour (7)
PIGMENT – PIMENT{o} = fruit, around G = good
54 Note British Romeo brought to First Lady (5)
BREVE – B = British, R = Romeo, EVE = first lady
55 Knight breaking legs in Cornish village (2,5)
ST AGNES – STAGES = legs, around N = knight
56 Persecuted boffin abandons grand Italian location (5)
TURIN – TURIN{g} = persecuted boffin
57 Harbour man soaked (9)
MARINATED – MARINA = harbour, TED = man
DOWN
1 Fun ignoring odds: score first-class century (5)
CRAIC – even letters in sCoRe, AI = A1 = first-class, C = century
2 Renewed plea about property — try vainly to settle debt (3,5,2,3,4)
ROB PETER TO PAY PAUL – (PLEA ABOUT PROPERTY)*
3 Arrange things on stage and explain situation (3,3,5)
SET THE SCENE – double definition
4 Improvement achieved in Bible class? (6)
REFORM – R.E FORM = Bible class
5 Joker perhaps is match for any character (4,4)
WILD CARD – double definition
6 One making meteoric progress — at Bisley? (8,4)
SHOOTING STAR – double definition
7 Mathematician to say graph needs modification (10)
PYTHAGORAS – (TO SAY GRAPH)*
8 Artist consuming little island dish (5)
RAITA – R.A. = artist, around AIT = small island
9 One can wind up eating this (9)
SPAGHETTI – cryptic definition
10 Bear out box containing Golden Fleece and ring (11)
CORROBORATE – CRATE = box, around OR = golden, ROB = fleece and O = ring
11 Aleppo man in houses of certain Arabs (5)
OMANI – hidden in AleppO MAN In
12 Continue to suppose parking unavailable (6)
RESUME – {p}RESUME = suppose
18 Dressing to conceal equipment constitutes crime (10)
BRIGANDAGE – BANDAGE = dressing, around RIG = equipment
20 Network girl coming north for Circle Line? (8)
DIAMETER – RETE = network, MAID = girl, all reversed
22 Trojan Horse for example making one tense? (10,7)
HISTORICAL PRESENT – double definition
23 Girl’s mother creates oppressive atmosphere (6)
MIASMA – MIAS = girl’s, MA = mother
24 Nut collector close to birch unearthed supply (4-6)
HEAD-HUNTER – {birc}H, UNEARTHED*
27 Sit one Oxbridge staffer in capsized ship (8)
POSEIDON – POSE = sit, I = one, DON = Oxbridge staffer. From the book (and film) The Poseidon Adventure.
31 Vatican right about small shock (6)
TREMOR – ROME = Vatican, RT = right, all reversed
32 Here’s the difference between buying and selling (6,6)
PROFIT MARGIN – (not even very) cryptic definition
34 Right-hand men coming round to impressive speaker (11)
RHETORICIAN – R.H. = right-hand, ERIC, IAN = men, around TO
36 Borscht, on us, prepared as seasonal treat (3,5,3)
HOT CROSS BUN – (BORSCHT ON US). No longer just for Easter – an extended seasonal treat that seems to arrive on shelves in January
37 Counter-agent: Napoleon’s man in England? (10)
SHOPKEEPER – double definition. England as “a nation of shopkeepers” is attributed to Napoleon
39 Daring disco dancing — with au pair? (9)
AUDACIOUS – (DISCO, AU, AU). Cleverly using “au pair” to suggest au twice
41 Distinctive theory about alternative meteorological line (8)
ISOTHERM – ISM = distinctive theory, around OTHER = alternative
45 Leads to instrument found in ship (6)
SPAWNS – S.S. = ship, around PAWN = instrument
46 Spread in book complete (6)
BUTTER – B = book, UTTER = complete
48 One bounds area between two American cities (5)
NYALA – N.Y. = American City, A = area, L.A. = American city
49 Turn out for Louis I in European court (5)
EJECT – E = European, JE = I for Louis (who is presumably French), CT = court
51 Be likely to cross river in general direction (5)
TREND – TEND = be likely to, around R = river
I started the puzzle in good humour with the (chestnut?) CORK’S CREW, and CRAIC followed to complete the Irish flavoured corner. One of those words which illustrates the Irish penchant for idiosyncratic spelling to confuse us Brits.
I’ve been to Bisley many times.