Across:
1 Served up (= reverse indicator) Mexican dish (taco = -OCAT-) in the foreign (the = el = L-E) (LOCATE) spot (LOCATE),
4 Nearly (n) overwhelm (‘stun’ without ‘n’ = STU-) with jobs in body shops (-DENTS) (STUDENTS) for potential school leavers (STUDENTS),
9 Sermonise dismissing REM (‘sermonise’ dismissing ‘REM’ = sonise = NOISES) and the awful sounds (NOISES),
10 All that remains (SKELETON) of a rough draft, in a writing sense (SKELETON),
12 Bells – a rum (bells – a rum = UMBRELLAS) blend? (= anagram indicator) For those stuck-up types on the beach! (UMBRELLAS),
13 Some takeover sensitive (some ‘takeover sensitive’ = VERSE) to Limerick (VERSE),
14 Domestic plot (GARDEN) is at the hub (CENTRE) (GARDEN CENTRE) of stock options for The Cherry Orchard (GARDEN CENTRE),
18 Describes King Cole (MERRY OLD SOUL) tipsy (MERRY) on aged (OLD) spirit (SOUL) (MERRY OLD SOUL),
21 Where you might find a stout type (stout drink = ON TAP) for Panto (Panto = ON TAP) adaptation (= anagram indicator),
22 Sounds like (= homophone indicator) confusing path (“maze” = “maize” = CORN-) for conservative (-C-) Playboy (-RAKE) (CORNCRAKE) bird (CORNCRAKE),
24 English (E-) and French men (Messeurs = -MM-) delayed (late = E-TAL) coming back (= reversal indicator) around mid-morning? (mid ‘morning’ = -N-) (EMMENTAL) Hard Cheese! (EMMENTAL),
25 Rugby player in the middle (CENTRE) of recent (recent = CENTRE) action (= anagram indicator),
26 Speculate (THEORISE) Kojak (THEO- Kojak) is to come back to life (-RISE) (THEORISE),
27 Gets on a train (BOARDS) at the end of 5 down (‘takes on board’ = BOARD-) going to school (-S) (BOARDS).
Down:
1 Crazy (= anagram indicator) angle (angle = LAN-GE) about leaders giving up argument (leaders “giving up argument” = -GUA-) (LANGUAGE) with English (LANGUAGE),
2 Glasnevin potato vines, for example (CLIMBERS), found on Mount Everest (CLIMBERS),
3 Subject (THEME) to helpmate getting rid of pal (‘helpmate’ getting rid of ‘pal’ = hemte = THEME),
5 Accepts (TAKES ON BOARD) this challenges the directors (TAKES ON BOARD),
6 Handed over (DELIVERED) legal document (deed = DE-ED) covering one of those producing bile (-LIVER-) (DELIVERED),
7 Sample covered up in a tureen (sample covered up ‘in a tureen’ = NATURE) of kidney (NATURE),
8 Suspects (SENSES) The Bishops are living there (bishop’s diocese/sees = SE -ES) over the school (National School = -NS-) (SENSES),
11 Those working on The Wire (ELECTRICIANS) produced lots of sparks (ELECTRICIANS),
15 The Observer (EYE) intro (OPENER) (EYE OPENER) is a revelation (EYE OPENER),
16 It’s not important (NO MATTER) why one can’t see The Invisible Man (NO MATTER),
17 Type of agents (SLEEPERS) holding up the train (SLEEPERS),
19 Humble (MODEST) Wordsworth works (-ODES-) in Montana (M-T) (MODEST),
20 Items (items = ST-MIE) discarded (= anagram indicator) around yard (-Y-) (STYMIE) in block (STYMIE),
23 The belief is (CREDO), there’s no gas to be found in God’s acre (there’s no ‘gas’ to be found in ‘gods acre’ = odcre = CREDO).