Across:
1 Clare (CE = C-E) consumes starters as near as possible (starters ‘As Near As Possible’ = -ANAP-) (CANAPÉ) to finger food (CANAPÉ),
4 Pity an (pity an) oddball (= anagram indicator) (pity an = -YPTIAN) following (= positional indicator), for example (e.g. = EG-) (EGYPTIAN), one of those in Africa (EGYPTIAN),
9 One of those on The Screen (CURSOR) from Rising (= reverse indicator), Revenue Commissioners (Revenue On-Line Service = ROS = -SOR) and old police force (Royal Ulster Constabulary = RUC = CUR-) (CURSOR),
10 Serves up (= reversal indicator) vegetable (leek = KEEL) range (oven) mostly (n) (‘oven’ without ‘n’ = OVE-) from recipe (-R) (KEEL OVER) and pass out (KEEL OVER),
12 Come across (TRACK DOWN) recording (TRACK) on The Blues (DOWN) (TRACK DOWN),
13 A signal to pick up (RADIO signal) a Dior (a Dior) dress (= anagram indicator) (a Dior = RADIO),
14 Got pregnant (-CONCEIVED) after being unwell (ILL-) (ILL-CONCEIVED) and it wasn’t planned with any great thought (ILL-CONCEIVED),
18 Ridiculous (= anagram indicator) rate for (rate for = REF-ATOR) taking in doctor (-RIG-) from hospital ward (-ER-) (REFRIGERATOR) where one keeps the bodies in the mortuary (REFRIGERATOR),
21 Reply (REACT) to ancestor’s missing sons (‘ancestors’ missing ‘sons’ = acestr = REACT),
22 Group of musicians (GARDA BAND) presumably familiar with the beat? (GARDA BAND),
24 One member of overseas Special Forces (SEAL) nearly (l) (‘seal’ without ‘l’ = SEA-) gets drunk at The Tap (WATER) (SEAWATER) – it holds the ship up! (SEAWATER),
25 Quarrel (F-IGHT) is over writing (from the 3Rs = -R-) (FRIGHT) that will give one the heebie-jeebies (FRIGHT),
26 Without a joint (SEAMLESS), it won’t have you in stitches (SEAMLESS),
27 Blind panic (TERROR) on first tee (first ‘Tee’ = T-) leads to inaccuracy (-ERROR) (TERROR).
Down:
1 Jasper is not part of practical jokes (‘Jasper’ is not part of ‘practical jokes’ = cticalok = COCKTAIL) in Manhattan? (COCKTAIL),
2 As a rule (NORMALLY), Molly ran (Molly ran) organisation (= anagram indicator) (Molly ran = NORMALLY),
3 Man in The Robe (monk) heading off (m) (‘monk’ without ‘m’ = -ONK) in pursuit of (= position indicator) place (PL-) (PLONK) to noisily put down (PLONK),
5 Eco-friendly (GREEN) grasses on local (‘grasses on’ local = betrays = FINGERS) (GREEN FINGERS) types employed in the nursery (GREEN FINGERS),
6 Cold, beastly type (POLAR BEAR) cut back (= reverse indicator) support to woman (bra = -AR B-) covering staff (pole = POL- -E-) leading artillery (leading ‘Artillery’ = -A-) regiment (-R) (POLAR BEAR),
7 Inadvisable to remove basil (‘ inadvisable’ to remove ‘basil’ = inadve = INVADE) or move into other parts of the plot (INVADE),
8 Not the first (‘Not’ the first = N-) pointer (-ARROW) (NARROW) tightly defined (NARROW),
11 They appreciate 22 across, for instance (CONCERTGOERS appreciate ‘Garda Band’), in the audience (CONCERTGOERS),
15 Uncork (OPEN) for heartless (t) Count? (total) (‘total’ = toal = TO AL) Port (port/left = -L) (OPEN TO ALL) from free bar presumably! (OPEN TO ALL),
16 Ill at ease (STRANGE-) with writing (from 3Rs = -R) (STRANGER) in The Outsider (STRANGER),
17 A stalker of The Animals (PREDATOR) and Teardrop (teardrop) Explodes (= anagram indicator) (teardrop = PREDATOR),
19 Conservative (C-) teacher (Sir) retires (= reversal indicator) (Sir = -RIS-) from institute (-I-) and school (-S) (CRISIS) in The Emergency (CRISIS),
20 Costa Rican neighbour (PANAMA), a (-A) worker (man = -NAM-) from press agency (Associated Press = PA-), retires completely (= reverse all letters) (PANAMA),
23 Grant (AGREE) said yes to (agreed) Trim? (trim/cut = ‘d’) (‘agreed’ without ‘d’ = AGREE).