Across:
1 Information technology (-IT-) firm (-CO-) involved in sadomasochism (S&M = S-M) (SITCOM) produced television comedy (SITCOM),
4 Includes (CONSISTS) overheads (CO-STS) covering new (-N-) school (-S-) on island (-I-) (CONSISTS),
9 Old (O-) tape (tape = -P-ATE) playing (= anagram indicator) contains single (-I-) (OPIATE) produced by The Chemical Brothers perhaps (OPIATE),
10 Pity an (pity an = -YPTIAN) oddball (= anagram indicator) following (= positional indicator), for example (e.g. = EG-) (EGYPTIAN), one of those in Africa (EGYPTIAN),
12 Star (SUN-) from The Shield (-SCREEN) (SUNSCREEN) offers protection to one of those getting tanned in Heat (SUNSCREEN),
13 What the copper would do with nitric acid (REACT) to give some feedback (REACT),
14 Family member (RELATION-) to post (-SHIP) (RELATIONSHIP) bond (RELATIONSHIP),
18 It’s difficult to catch (WILL-O-THE-WISP) testament (WILL -) from The Bible (Old Testament = -O-T-) by that man (-HE-) with small bunch of hay (WISP) (WILL-O-THE-WISP),
21 Tourist is removed (‘tourist’ ‘is’ removed = tourt = TROUT) from the fish farm (TROUT),
22 You’re presumably looking at this right now (CROSSWORD), annoyed (CROSS-) by a single conversational piece (-WORD) (CROSSWORD),
24 Keep the lid on local (‘keep the lid on’ is local/informal for RESTRAIN) getting about (RE-) on small (-S-) mode of transport (-TRAIN) (RESTRAIN),
25 Little devil (HORROR) from The Bride of Frankenstein, for example (Bride of Frankenstein = HORROR film),
26 Ocean liner (SAND) reaches Dublin (D-) with a French (a = -UNE) (SAND DUNE) formation synonymous with Oasis (SAND DUNE),
27 Finish (ENAMEL) Le Mans (Le Mans) getting clipped (s) (‘Le Mans’ = without ‘s’ = leman) by English leader (‘English’ leader = E-) going the wrong way (= reversal indicator) (‘leman’ = -NAMEL) (ENAMEL).
Down:
1 Backs (SPONSORS) those with their corporate characters all over Jersey (corporate characters/logos all over football jersey = SPONSORS),
2 Obtuse type of figure (obtuse TRIANGLE) produced poor result (poor result/no grade = -NG-) in court case (TRIA-L-) and that’s key (music key -E) (TRIANGLE),
3 Awkward (= anagram indicator) topic (topic = OPTIC) for one on the bottle in the pub (OPTIC),
5 Group of (ORGANISATION) newspapers (ORGAN-S-) covering one (-I-) country (nation) with no leader (‘nation’ without ‘n’ = -ATION) (ORGANISATION),
6 Criminal (= anagram indicator) uses Viper (uses Viper = SUPERVISE) as guide (SUPERVISE),
7 Shreds (rips = SPIR-) reviews (= reversal indicator) for leads from Abbey, Lyric (leads from ‘Abbey, Lyric’ = -AL) (SPIRAL) and Helix (helix = SPIRAL),
8 Pick out (SE-E) shady type (tan = -NAT-) turning up (= reversal indicator) inside (SENATE) the house (SENATE).
11 It’s about (RE-) picking up on what the artist produced (-COLLECTION) (RECOLLECTION) from memory (RECOLLECTION),
15 Social network (TWITTER-) editor (-ED) (TWITTERED) went on and on (TWITTERED),
16 Weighty type (KILOGRAM) of review? (= reversal indicator) Margo (Margo = -OGRAM) gets to like (like) most of it! (most of ‘like’ = lik = KIL-) (KILOGRAM),
17 Takes the pain out of delivering (EPIDURAL) papers (-ID-) in Peru (Peru = EP-UR-) ordered (= anagram indicator) by gangster (-AL) (EPIDURAL),
19 Sailor (-TAR-) has time (-T-) in boat (S-S) (STARTS) for the new jobs (STARTS),
20 In relation (COUSIN) to documentaries dismissing red meat? (‘documentaries’ dismissing ‘red meat’ = ocunis = COUSIN),
23 Contempt (SCORN) for scoundrel losing duel (‘scoundrel’ losing ‘duel’ = sconr = SCORN).