ACROSS
1 Chauffeur says chef has regular absences (4)
SYCE – S{a}Y{s} C{h}E{f}
3 Judges protecting intellectual property with very good software, a source of material for Panama (5-5)
JIPPI-JAPPA – J J [(two) judges] “protecting” IP PI [intellectual property (with) very good] + APP A [software | a]
This is an Ecuadorean palm fibre from which Panama hats are made. If you thought Panama hats were made in Panama you’ve got another think coming!
9 Subordinate officer wearing cap seizes good part of fisherman’s catch (7)
LINGCOD – NCO [subordinate officer] “wearing” LID [cap] “seizes” G [good]
11 Folio’s replacement for line in wrinkly hag’s description of ronyon (4-3)
RUMP-FED – RUMP{l->F}ED [wrinkly, with L = line replacing F = folio].
Macbeth, Act 1, Scene 3: “Aroint thee, witch!” the rump-fed ronyon cries.”
12 Clutching spike, endlessly attack sociological writer (9)
MARTINEAU – “Clutching” TINE [spike], MARAU{d} [“endlessly” attack].
Harriet Martineau, perhaps the first female sociologist, notable works including “Illustrations of Political Economy” (1834)
13 Straw bundles for some Taxus-Ulmus grafts? (5)
YELMS – the Taxus being the YEW, and the Ulmus the ELM, splice them together to find the answer.
14 Forensic anthropometry is to occur right up to the time of working period (12)
BERTILLONAGE – BE R TILL ON AGE [to occur | right | up to the time of | working | period]
Bertillon is referenced in The Hound of the Baskervilles as being an even greater expert than Holmes, that’s how great a criminologist he was.
18 Waltz Matilda’s sulking about diminished melancholy (4,3,5)
HUMP THE BLUEY – HUMPY [sulking] about THE BLUE{s} [“diminished” melancholy]
21 Wife to judge the weight of hoisted cloth (5)
WHEFT – W HEFT [wife | to judge the weight of]
22 Piercing rock backing was profitable and is welcomed by half of Iron Maiden (9)
DIAPIRISM – reversed PAID [was profitable] + IS “welcomed” by IR{on} M
24 Historically, a hundred are incapable of umpiring (7)
CANTREF – double def’fed with CAN’T REF [are incapable of umpiring]
25 Oscar in works for a famous actor? (7)
ROSCIAN – (OSCAR IN*) [“works”]. Roscius was a famous Roman actor of the 1st century BCE. I used to catch a bus home through Crystal Palace past a blue plaque dedicated to Ira Aldridge, the 19th century theatre’s “African Roscius”.
26 Meat wagon utterly pointless before strange band of urchins? (10)
AMBULACRUM – AMBULA{n}C{e} [meat wagon, with all of its compass points subtracted] + RUM [strange].
Not multiple urchins, but the radial band in the shell of an echinoderm allowing its tube-feet to protrude.
27 Light carriage opposed by Huxley’s second novel? (4)
CHAY – because Huxley’s second novel was Antic Hay, anti-chay, do you see?
DOWN
1 Flaubert’s novel strike in Russian-style wrestling (8)
SALAMMBO – LAM [strike] in SAMBO [Russian-style wrestling]
2 Film-related item seldom seen without it containing burnt corpses? (8)
CINERARY – CINE [film-related] + RAR{it}Y [item seldom seen, minus IT]
4 Provide with rear shade in the East End (5)
INDUE – or ‘ind ‘ue [rear | shade] as pronounced by someone dropping all their aitches.
5 For each marooned sailor, a hotel in Indian subdistrict (9)
PERGUNNAH – PER GUNN A H [for each | marooned sailor | a | hotel]
Ben Gunn was marooned for years on Treasure Island, during which time he naturally developed an obsessional craving for cheese.
6 Smackers slash old, ugly mischief-makers (5-8)
JIMMY O’GOBLINS – JIMMY [slash, as in Jimmy Riddle] + O GOBLINS [old | ugly mischief-makers]. Lots of Cockney rhyming slang in this puzzle! For apparently this is a rhyme for “sovereigns”. And you thought the occasional dodgy homophone in the 15×15 was bad…
7 Cock, very loud, interrupting nap (6)
PIFFLE – FF [very loud], “interrupting” PILE [nap]. “Cock” as in “nonsense”.
8 Type of sugar parties put in beer (6)
ALDOSE – DO’S [parties] “put in” ALE [beer], straightforwardly enough
10 Double curl in it, a variant of hair growth (13)
CRINICULTURAL – (CURL CURL IN IT A*) [“variant”]
15 Petrifying chapter, even though I had one friend standing up (9)
LAPIDIFIC – reverse all of C IF I’D I PAL [chapter | even though | I had | one | friend]
16 After slander, current successor backed governor’s office (8)
MUDIRIEH – after MUD [slander], I [current] + reversed HEIR [successor]
17 Who said to follow the van shedding load? Extremely cheeky mice may show what’s to come in it (8)
MYOMANCY – MY O{ld} MAN [from the 1919 music hall song, minus LD = load] + C{heek}Y
19 African rhino caught in grip of soaring alpha predator of the skies (6)
KWACHA – C [caught] “in grip of” reversed A HAWK [alpha | predator of the skies]. Rhino as in (Zambian/Malawian) money, of course.
20 Perhaps Munro and Corbett inverted pods used for dyeing (3-3)
NEB-NEB – Munro and Corbett are two BENs, put them together and reverse.
23 Twentieth-century player of piano music arranged by Gold (5)
ARRAU – ARR. [arranged] by AU [gold]. Chilean virtuoso pianist Claudio Arrau.
V, you have a problem with your entry at 5dn which has made everything thereafter stay in italics .. I suspect the </u> should be </i>
Much of the rest needed to be chiselled out from the cryptic stuff, and it took a long time, around an hour and quarter. But it was enjoyable wrestling.