Although the wordplay was accessible, the vocabulary was rather stretching. As your selfless blogger, I’ve checked in the dictionary as needed. Perhaps this setter is submitting his credentials for the Mephisto? Thanks to him/her for a very enjoyable puzzle.
Clues are in blue, with definitions underlined. Answers are in BOLD CAPS, then wordplay. (ABC*) means ‘anagram of ABC’. Deletions are in [square brackets].
Across
1 Embarrassed about lines being revoked (8)
REVERSED: RED “about” VERSE. I said it was easy!
9 Isn’t without sensitivity, initially, one partner being this? (8)
INTIMATE: I[s]NT (without sensitivity, initially), I (one), MATE (partner). Literal definition.
10 Boundary stone, yellow lump of rock (6)
METEOR: METE, OR (yellow, in heraldry and crosswords). The first dictionary call. Yes, “mete” can mean “boundary”. I can see it is a sensible extension of the “measure” meaning of “mete”.
11 Ring maybe to confirm this appointment (10)
ENGAGEMENT: cryptic definition.
12 Stuff written on back of book, mostly obscure (4)
BLUR: BLUR[b].
13 Something toxic in bottle given to spy (5,5)
NERVE AGENT: courage, spy.
16 Mention train (5,2)
BRING UP: double definition. Another dictionary call confirms “to rear or educate” as a definition of “bring up” that fits “train” well enough.
17 List former police force sent around seen in Guardian (7)
CURATOR: ROTA, R.U.C., all “sent round”.
20 Officers looking after sections of prison? Idiots! (10)
BLOCKHEADS: ho ho … heading prison blocks, geddit.
22 Heartless German philosopher viewed as despicable person (4)
HEEL: HE[g]EL. Do I detect irony here?
23 The police needing to travel by air ultimately? Here’s the answer (10)
HELICOPTER: anagram (“travelling”) of (THE POLICE*), then [ai]R. Another literal definition.
25 Spoil the atmosphere, backing one up to no good (6)
IMPAIR: AIR “backing” IMP.
26 Mute individual welcomed finally into community (4,4)
TONE DOWN: ONE [welcome]D “into” TOWN. “Mute” seems stronger than “TONE DOWN” to me.
27 Odds and ends in newspaper by hard-line Tories (8)
SUNDRIES: Sun, Dries.
Down
2 Former English politician having endless fun as model (8)
EXEMPLAR: EX, E, MP, LAR[k].
3 Note cleric getting troubled using a computer? (10)
ELECTRONIC: anagram (“getting troubled”) of (NOTE CLERIC*).
4 Having sufficient confidence, as you’d expect (4,6)
SURE ENOUGH: double definition.
5 Those down under enjoy American composer, not half! (7)
DIGGERS: DIG, GERS[hwin].
6 Caveman‘s hidden in forest, I guess (4)
STIG: hidden answer. I’d never heard of this chap – obviously after my time.
7 Cluster in athletics event with yours truly coming last (6)
RACEME: RACE, ME. Dictionary please? Not sure I’m much the wiser! It says:
raceme /ra-, rə- or rā-sēmˈ, or rasˈēm/ (botany)
noun
An inflorescence in which stalked flowers are borne in acropetal succession on a main stalk or lateral branches
A similar group of spore-cases
ORIGIN: L racēmus a bunch of grapes
8 One with will to try a climbing challenge on Dartmoor? (8)
TESTATOR: TEST, A, TOR.
14 Plea to have leader brought down, man on horseback (10)
EQUESTRIAN: REQUEST with the R moved to the end, then that good fellow IAN.
15 Axes may be put down on this (5,5)
GRAPH PAPER: cryptic definition. Not, the axes aren’t in the woodpile out the back! They are the X axis and Y axis of the graph.
16 Quail, seeing chess player opening with quick move (8)
BOBWHITE: BOB (quick move), WHITE (chess player). The dictionary confirms it’s an American quail. Didn’t know it.
18 Get excessively weary, showing obvious anger (8)
OVERTIRE: OVERT, IRE.
19 Birds wanting spoils, eating loaf of bread (7)
MARTINS: TIN in MARS. I understand “tin” or “bread” is slang for “money”, but don’t know what the loaf is doing here, but perhaps a “tin loaf” is a way of cooking bread?
21 Where to sign to be connected to network (6)
ONLINE: double definition. Sign on the dotted line, traditionally. Or, get online. On edit: as jackkt points out, perhaps “where to sign” is a hint rather than a definition. For one thing, its enumeration would be (2,4), not (6).
24 Gong drowning old wind instrument (4)
OBOE: O in OBE.
I found this relatively straightforward, helped by knowing everything except BOBWHITE.
FOI ENGAGEMENT
LOI BOBWHITE
COD BRING UP (although, like Bruce, I liked HELICOPTER)
TIME 7:40
Not that it matters particularly but I don’t think 21dn qualifies as a double definition. The first part is more of a cryptic hint leading to the answer and it would require different enumeration (2,4).
Edited at 2019-06-21 11:25 pm (UTC)
A tin is the name of a loaf of bread .. a loaf made in a tin and thus retaining that shape.
The ODO definition of raceme is a bit more accessible than that quoted: “A flower cluster with the separate flowers attached by short equal stalks at equal distances along a central stem. The flowers at the base of the central stem develop first.”
A foxglove would be a classic example.
STIG of the Dump featured fairly prominently in my childhood both as a book and a TV series.
Like Kevin I got BOBWHITE partly by thinking of BOBOLINK, which was one of Jeff Pearce’s favourite birds.
FOI 1dn EXEMPLAR
LOI 23ac HELICOPTER – my son Jack for years referred to this flying machine as a HECILOPTER!
COD and WOD 16dn BOBWHITE
45 minutes
Just under the hour to complete this having breakfast whilst car being serviced. Like the blogger, didn’t untangle the simples clue at 1a until quite late in the piece. Hadn’t seen STIG, METE or the BOBWHITE before, but all easy enough to work out and check.
As it turns out STIG was the first one in and the other two were the last two.