Across:
8 Heard (= homophone indicator) Moore (“Moore” = “moor” = -HEATH) joins society (S-) first (= position indicator) (SHEATH) – it’s a cover up (SHEATH),
9 Retiring (= reversal indicator) fiction writer (liar = RAIL-) from one of the clubs (one of the clubs = one club -CARD from playing cards) (RAILCARD) guarantees a cheaper fare for The Orient Express (RAILCARD),
10 Bank’s allowable expenses (banks/sides “allowable expenses” = ALES) for a few beers (ALES),
11 Suppressions (CLAMPDOWNS) of presses (CLAMP-S) around county up north (-DOWN) (CLAMPDOWNS),
12 Had a lot to say in Rome (CICERO) to officer (commanding officer = C-O) covering up rice (rice = -ICER-) production (= anagram indicator) (CICERO),
14 He paints (he paints = THESPIAN) swing (= anagram indicator) in the cherry orchard (in Anton Chekhov’s The Cherry Orchard = THESPIAN),
15 Most of those (s) in 26 across (“greens” without “s” = GREEN-) park (-FIELD-) on spots (SITES) (GREENFIELD SITES) and places awaiting developments (GREENFIELD SITES),
18 Cut top (s) herb (“sage” without “s” = AGE) bunch (GROUP) (AGE GROUP) from a similar vintage (AGE GROUP),
20 Primate leaves prayer meeting (“primate” leaves “prayer meeting” = yereng = ENERGY) with enthusiasm (ENERGY),
22 Detailed outlines (BLUEPRINTS) of music (Blues = BLUE-S) cover for reproduction (-PRINT-) (BLUEPRINTS),
24 Haul (loot = TOOL) up over (= reversal indicator) device (TOOL),
25 Those in Croke Park (STANDS) popular (IN) (STANDS IN) with substitutes (STANDS IN),
26 Olive’s (olives = GREENS) found at the end of 13 down (“evergreens”= GREENS).
Down:
1 Catholic (C-) hospital (-H-) for the sick (-ILL) gets unit (-I) (CHILLI) that’s a hot addition to any place where there’s consumption (CHILLI),
2 Falling out (spat = TAPS) over (= reversal indicator) watery types in the kitchen (TAPS),
3 Put a tick against (CHECK OFF) Russian writer (“Chekhov” = “CHECK OFF”) for the audience (= homophone indicator),
4 Operatic song (ARIA) from familiar film is missing (from “familiar” “film” is missing = “familiar” without “film” = aiar = ARIA),
5 Spot (PIMPLE) foreign politician (-MP-) accommodated in stately home (pile = PI-LE) (PIMPLE),
6 Account (AC-) by Joker (-COM-IC-) locking up place (-PL-) for Oriental (east = -E) (ACCOMPLICE) partner in crime (ACCOMPLICE),
7 Face it (FRONTAGE), it’s perfect for window-shopping (FRONTAGE),
13 Under no circumstances (never) lose head (n) (“never” without “n” = EVER-) at party (-GREENS) (EVERGREENS) with The Hollies (EVERGREENS),
14 24 down (tied) almost (d) (“tied” without “d” = TIE-) provides starts for unemployed people (starts for/first letters of “unemployed people” = -UP) (TIE-UP) to link together (TIE-UP),
16 Keep tabs on (REGULATE) police (REGULATE),
17 Decorate (DRESS-) with precious material (silver = -AG-) from Spain (-E) (DRESSAGE) for Arabian display, for example (Arabian/horse display, for example = DRESSAGE),
19 Aggressor loses rag (“aggressor” loses “rag” = gessor = OGRESS) with monstrous female (OGRESS),
21 A selection of drinks (-ROUND) after (= positional indicator) golf (G-) (GROUND), of course (course = GROUND),
23 The sisters (NUNS) of Erica not getting into insurance (“Erica” not getting into/missing from “insurance” = nsun = NUNS),
24 Bound (TIED) to change (= anagram indicator) diet (diet = TIED).