No 12857, Thursday 13 Feb 2020, Gridman

ACROSS
1   Believes car, shaking, can still be used (11) SERVICEABLE*
9   I’ve driven away depression, it’s clear (7) EVIDENT {IVE*}{DENT}
10 Hide the French heart-throb (7) LEATHER {LE}{HEART*}
11 Father has disturbed a high-ranking officer (5) PASHA {PA}{HAS*}
12 Late on transplanting a tree but free from blame (9) EXONERATE {EX}{ON}{A+TREE}*
13 Six in short film are very bright (5) VIVID {VI}{VIDeo} (Addendum - {VI{VI}Deo} See comments)
15 Actions in order for Italian conductor (9) TOSCANINI*
18 Paris priests follow others for these treatments for exhaustion (4-5) REST-CURES {CURES}* after {REST}
21 One girl, fallen back in stormy sea, gets support (5) AEGIS {1} after {G} in {SEA}* (Addendum - {1}{G}<= in {SEA}* - See comments)
22 Such a day is sure to be sunny with no chance of rain (9) CLOUDLESS [CD]
24 Learner is suffering, it’s obvious (5) PLAIN {P{L}AIN}
26 Blazing big — somebody’s going round tree (7) BONFIRE {B}{ON{FIR}E}
27 A couple of learners produce back issue that’s not just recent (3-4) ALL-TIME {A}{LL}{EMIT<=}
28 Clarify viewpoint after detective inspectors break net (11) DISENTANGLE {ANGLE} after {DIS}{NET*}

DOWN
1   When it’s time to get up apparently at friend's after having stayed the night? (9) SLEEPOVER {SLEEP}{OVER}
2   Rules announced to bring in means of control (5) REINS (~reigns)
3   Cecil and I used foreign language (9) ICELANDIC*
4   Appeal from centre a travesty (7) ENTREAT [T]
5   Screams from companions exchanging female for boy (7) BELLOWS (-f+b)BELLOWS
6   To some extent, tried a ventriloquist’s set-up dodge (5) EVADE [T<=]
7   Sharp fall in good use of exact words used in expressing a thought (8) PHRASING {SHARP*}{IN}{G}
8   Ringleader, about whom there’s a charge, is at large (4) FREE {F{Ri...r}EE}
14 Nobleman’s calls — half of them matter (8) VISCOUNT {VISits}{COUNT}
16 A head backs everybody holding exercise in music without accompaniment (1,8) A CAPPELLA {A}{CAP}{ALL<=} over {PE}

17 Perhaps nicer in incomplete set? That’s hypocritical (9) INSINCERE {IN}{S{NICER*}Et} (Addendum - {NICER+IN+SEt}* - See comments)
19 Alludes to having eastern joints (7) REEFERS {RE{E}FERS}
20 Back Mark hosting American (7) SUSTAIN {S{US}TAIN}
22 Solid figure crumbled at intervals (4) CUBE {CrUmBlEd}
23 Towelled and having no sweat, passed over summer’s end (5) DRIED {D{s...eR}IED}
25 Furious — Red leader isn’t showing sign of growing mature (5) AGING rEGING

Reference List
The Frensh = LE, Father = PA, Late = EX, French priest = CURE, Girl = G, Learner = L, Big = B, Detective Inspector = DI, Female = F, Boy = B, Good = G, Exercise = PE, Eastern = E

Dr RKE's TalePiece

An AGING VISCOUNT was prescribed a REST CURE. He handed over the REINS to his deputy and went for a SLEEPOVER in the house of a PASHA.  It was EVIDENT that there would be no drizzle on such a CLOUDLESS night. So an alfresco dinner was arranged under the AEGIS of a wealthy sponsor. A BONFIRE, SUSTAINed and stoked by BELLOWS kept them warm and mellow. The live band played songs from that famed ICELANDIC composer Jón Leifs, in the ALL TIME great TOSCANINI style, but A CAPELLA.  The viscount plonked himself on a plush LEATHER lined chair and sipped his single malt with just one CUBE of ice. It was rumoured that DRIED REEFERS were also passed around, elevating the mood.  Thus, the viscount could DISENTANGLE himself from the cares of a peer's life, and thankfully be FREE from the nagging by his countess. He gradually drifted to a blissful sleep in which he had VIVID dreams of cute young things ENTREATing him for an assignation!  Was he EXONERATEd for such an INSINCERE act, albeit in a dream? The PLAIN PHRASING of the divorce notice told it all !