Monthly Club Special 20,251: Slubberdegullions Need Not Apply

I found this quite a beast to solve, but a very enjoyable one, full of literally incredible words from all around the globe. 18ac looks like a basic cluing error to me, unless anyone can prove otherwise, but I really liked some of the elegant constructions elsewhere: 12ac is a sweet anagram, and I loved the clever way of reimagining the word anisette at 28ac, the use of Dorian Gray at 22ac, and 14ac finding a way to begin and end with a racket. Nothing wrong with the down clues either, with RHYNCHOBDELLIDA being todays’s word to “take the cake”. Apparently these are leeches with “proboscis but no jaw” so I will pronounce 5dn to be jaw-dropping.

Thanks to the setter for our mensal mental workout!

Definitions underlined, (ABC)* indicating anagram of ABC, {} deletions and [] other indicators.

Across
1 French out of competition over early transit option (8)
HORSECAR – HORS [French “out of”] + reversed race [competition, “over”]
6 Muslim teacher and king scuttle German agreement (6)
KHODJA – K HOD JA [king | scuttle | German “yes”]
9 Concealing their ends, everyone prompting adviser to Charlemagne (6)
ALCUIN – AL{l} CUIN{g}. I know this best as a college at York University
10 Very important to restrict string length round bunting (8)
YELDROCK – KEY “restricting” CORD L, the whole reversed. Same as a “yoldring”, according ot the dictionary, which I’m sure helps a lot
11 Leave Home Secretary to reverse country’s sway (4)
SHOG – GO H.S., the whole reversed. Dialect for shake, sway, jog, that kind of thing.
12 Sweet tempered raconteuse (10)
NECTAREOUS – (RACONTEUSE*)
14 Racket’s target? Thug renouncing a racket (8)
BALLYHOO – BALL [(tennis) racket’s target] + Y{a}HOO
16 Dress to the left, nearly showing basket of mine? (4)
CORF – FROC{k} reversed. A coalminer’s basket, when it isn’t a lobster cage.
18 Decorated case recalled in lawsuit evidence (4)
ETUI – hidden but not hidden in {laws}UIT E{vidence}. Is this simply an error?
19 Adviser against imitating the past, the man had backtracked (8)
DEHORTER – RETRO HE’D, reversed. The rarely seen opposite of an exhorter
21 See many in the mirror injecting an ounce that enhances athletic performance (10)
STANOZOLOL – LO LOTS, reversed, “injecting” AN OZ. Wouldn’t “in the mirror” turn the Ls and S back to front too? A performance-enhancing drug probably used by Stanislavski when he needed to portray a muscly athlete onstage [citation needed]
22 Excessive indulgence of almost the first couple in Dorian Gray (4)
ORGY – {d}OR{ian} + Gy [abbreviation for the SI unit of absorbed dose of ionizing radiation]
24 For old tragedian, boots banal stuff around day one (8)
COTHURNI – CORN around THU, plus I. Kothornoi, the tragic buskins, came up a lot in my time as an undergraduate doing Lit Hum
26 Perhaps rustle from aged subordinate officer stops during the last month (6)
UNCOLT – N.C.O. “stops” ULT. Shakespearean or thereabouts for “to deprive of a horse”
27 Note a vaccination involving hospital about which Hindus sing (6)
BHAJAN – N A JAB “involving” H, all reversed. Quite different from a bhaji
28 Cordial missive from Folketing possibly avoiding extremes (8)
ANISETTE – {d}ANIS{h} {l}ETTE{r}
Down
2 Official staff raise Henry and Maureen informally (5)
OMLAH – HAL + MO reversed. A “staff of officials” in India, that’s human staff not a sceptre as far as I can make out.
3 American’s watery stew of (I’m thinking) chump eaten by small cat (11)
SLUMGULLION – UM… GULL “eaten by” S LION
4 Blue worn by new cook reduced problem in throat (8)
CYNANCHE – N “wearing” CYAN + CHE{f}. Quinsy seems to be a vernacular rendering of this handsome Greek word which means something like “dog-throttler”
5 Confusion of inch and yard when checking rustic valley leeches (15)
RHYNCHOBDELLIDA – (INCH + YARD*) “checking” HOB DELL
6 Hookah by another name, mostly secured by knots (6)
KALIAN – ALIA{s}, “secured” by KN. [the nautical measure]
7 Rise of Australian native related to us in Perth (3)
OOR – reversed ROO. Who else remembers “Oor Wullie”? And/or The Broons?
8 Introduction of Justice Bill baselessly expresses doubt about revolt (9)
JACQUERIE – J{ustice} + A/C + QUERIE{s}
13 Mark of injury, mark that’s painful, in eastern European’s forgotten battle (11)
ESCARMOUCHE – SCAR M OUCH, in E E. Old spelling of skirmish it looks like
15 I can’t digest a superior serving of brandy, say, pub having run out earlier (9)
AUTOTROPH – A U TOT, plus P.H. after RO. An organism that generates its chemical constituents from simple inorganic compounds, rather than by ingesting things, I guess
17 After British aid, India supports old city, providing some local food (8)
BHELPURI – after B HELP, I supports UR. Indian puffed rice with onions, which sounds quite nice; FOI
20 Domestic office covering reservation reared antelope (6)
DZEREN – DEN “covering” reversed REZ, as in a native American reservation
23 Forced exile is to saturate surrounding area (5)
GALUT – GLUT “surrounding” A. A Hebrew word meaning the forced exile of Jews from, e.g., Palestine
25 Elevation of God in Rastafarianism or Islamic expectation (3)
HAJ – JAH reversed: one of the Five Pillars of Islam