Across:
8 Some plain sobriety (some ‘plAIN SOBriety’ = ainsob) doing the rounds (= reverse indicator) (ainsob = BOSNIA) in Eastern Europe (BOSNIA),
9 Hostile (INIMICAL) up (= reverse indicator) north (NI = IN-) to institute (-I-) taking idiotic (= anagram indicator) claim (claim = -MICAL) (INIMICAL),
10 Concealed by psychopath you’d (‘psychopATH Yud’ = ATHY) come across in Kildare (ATHY),
11 Opposition (ANTITHESIS) to atheists in (atheists in) Order (= anagram indicator) (atheists in = ANTITHESIS),
12 It’s in the blood (PLASMA) raising (= reversal indicator) sheepish types (rams) off the summit (r) (‘rams’ without ‘r’ = ams = -SMA) on mountain (alp = PLA-) (PLASMA),
14 Digs up (= reverse indicator) part of green (bed = DEB-) behind (= position indicator) back of ground (back of ‘grounD’ = -D-) in cricket clubs (bats = BA- -TS) (BAD DEBTS) – the types that are written off by all accounts (BAD DEBTS),
15 The little gifts suspended at Christmas (STOCKING FILLERS) produced by leggy types presumably? (STOCKING FILLERS),
18 Describes the filthy stuff (FOUL) from The Rose Tattoo (Tennessee Williams’ The Rose Tattoo = PLAY) (FOUL PLAY) investigated by the Guards (FOUL PLAY),
20 Turns up (= reverse indicator), Irene (Irene) loses heart (e) (‘irEne’ without ‘e’ = irne = ENRI-) to Charlie (-C-) Henry (-H) (ENRICH) – how is that better? (better = ENRICH),
22 Sharp tone (ASTRINGENT) in article (A-) by freelancer (stringer), for the most part (r) (‘stringer’ without ‘r’ = -STRINGE-), is not (not) heartless? (‘o’) (nOt’ without ‘o’ = -NT) (ASTRINGENT),
24 Baldwin dismissed ban (‘Baldwin’ dismissed ‘ban’ = ldwi = WILD) as uncivilised (WILD),
25 Sized up the length of (MEASURED) rattlesnakes on top of (‘Rattlesnakes’ on top of = -R-) exotic head (‘Exotic’ head = -E-) carried by wild (= anagram indicator) Medusa (Medusa = MEASU-D) (MEASURED)
26 Passing note disregarding spies (‘passing note’ disregarding ‘spies’ = angnot = TONGAN) from friendly island (TONGAN is from Tonga or The Friendly Islands).
Down:
1 Once, having left Monte Carlo (‘once’ having left ‘Monte Carlo’ = mtarlo = MORTAL), received a deadly blow (MORTAL),
2 Be resentful of (ENVY) English ivy on the borders (‘ENglish iVY’ on the borders = ENVY),
3 A (-A-) false (= anagram indicator) alarm (alarm = -LAMAR-) in Channel Islands (CI = C-I) (CALAMARI) producing seafood (CALAMARI),
4 Banks disclosure statement (banks ‘DIsclosure statemeNT’ = DINT) leads to depression (depression/indent = DINT),
5 Joined (FITTED) LinkedIn (LinkedIn), in a manner of speaking (= homophone indicator) (‘LinkedIn’ = ‘linked in’ = FITTED),
6 21 down (‘cellar’ = CELLAR) follows (= position indicator) 24 down (‘wine’ = WINE) (WINE CELLAR) and plonks down here perhaps? (plonk’s down here/wine’s down here in WINE CELLAR),
7 Caught (C-) knocking back (= reverse indicator) one of those in 6 down perhaps from Greece (one of those in ‘wine cellar’ = Retsina = -ANISTER) (CANISTER) out of container (CANISTER),
13 Profane belief (SECULARISM) in Lear’s music (Lear’s music) melody (= anagram indicator) (Lear’s music = SECULARISM),
14 The swingers hope to avoid this (swingers/golfers hope to avoid BOGEY) marsh (BOG-) near centre of Keys (centre of ‘kEYs’ = -EY) (BOGEY),
16 Repository of the hammer and sickle (TOOL SHED) and revolutionary (= reversal indicator) proceeds of crime (loot = TOOL) to cast off (SHED) (TOOL SHED),
17 Name (IDENTITY) one (I-) key (music key -D-) living thing (-ENTITY) (IDENTITY),
19 Those in solitary confinement (LONERS) or on the outside? (LONERS),
21 Is getting out of Carlisle (‘is’ getting out of ‘Carlisle’ = carlle = CELLAR) for a basement in Bordeaux (CELLAR),
23 Starting off (b) gives in (bends) (‘bends’ without ‘b’ = ENDS) to objectives (ENDS),
24 A press release (WINE) produced by drinks manufacturer (WINE).