Across:
1 To cross Swords (to cross swords/argue = BICKER), motorcyclist (BI-KER) went over 100 (Roman 100 = -C-) (BICKER),
4 Show of hands (APPLAUSE) for the pit workers, for instance (APPLAUSE for orchestra in pit),
9 Small (S-) admission (-ENTRY) (SENTRY) by one of those at The Gate (SENTRY),
10 You’d expect footballers to be in possession of this (club land = CLUBLAND) in area where some make movements to score? (dance to score/music = CLUBLAND),
12 Leaves home (TREE) and joins wedding band (RING-) – lead singer (lead singer = -S) (TREE RINGS) is helping those in 13 across with dating (TREE RINGS helping ‘trees’ with dating/the age of trees),
13 Recreates without care (‘recreates’ without ‘care’ = retes = TREES) for Holly and Hazel (TREES),
14 Address (PRESENTATION) of the sisters (PRESENTATION Sisters),
18 Worker (MAN-) is first to undertake (first to ‘Undertake’ = -U-) a number of assignments (-MISSIONS) (MANUMISSIONS) historically setting people free (MANUMISSIONS),
21 Dismiss (LET GO) those starting (‘Those’ starting = -T-) in the building game (lego = LE- GO) (LET GO),
22 Made less relaxed (TIGHTENED) by dental hygienist removing inlays (‘dental hygienist’ removing ‘inlays’ = denthgiet = TIGHTENED),
24 One (I-) American university (Massachusetts Institute of Technology = -MIT-) reviews (= reverse indicator) lists of duties (rota = -ATOR) (IMITATOR) of plagiarist (IMITATOR),
25 Turns up (= reverse indicator) a (-A) long (-L-) spring (leap = PAEL-) (PAELLA) is a favourite in the Spanish restaurant business (PAELLA is a favourite in Spanish restaurant business),
26 Remove fat (DEGREASE) as agreed (agreed), cooking (= anagram indicator) (agreed = DEGREA-) starters with scrambled eggs (starters with ‘Scrambled Eggs’ = -SE) (DEGREASE),
27 Works at the gate (plays at The Gate Theatre = PLAY-S) guarding a (-A-) (PLAYAS) space for loungers in Barcelona (loungers on Spanish beach / PLAYAS).
Down:
1 Submarine (sub) rises (= reverse indicator) (sub = BUS) to the top of the sea (the top of the ‘Sea’ = S-) and heads (-TOPS) (BUS STOPS) for shelters at various stages (BUS STOPS),
2 Admits (CONCEDES) Grant (-CEDE-) is taken in by tricks (tricks/cons = CON-S) (CONCEDES),
3 It’s a mistake (ERROR) losing the head (t) with local rascal (‘terror’ without ‘t’ = ERROR),
5 Exerts influence in secret (PULLS STRINGS) for Yanks (yanks = PULLS) from 20 down (‘string’ = STRING-) on bender (-S bend) (PULLS STRINGS),
6 Offerings of drinks (LIBATIONS) produced by Cricket Club (bat = -BAT-) – the first from India (the first from ‘India’ = -I-) welcomed by those with pride (lions = LI-ONS) (LIBATIONS),
7 Country (USA-) ends appalling practice nowadays (ends ‘appallinG practicE nowadayS’ = -GES) (USAGES) of accepted conventions (USAGES),
8 Adam (ELDEST) and Ray from steel yard (‘Ray’ from ‘steel yard’ = steeld = ELDEST),
11 Orders (INSTRUCTIONS) lessons? (INSTRUCTIONS),
15 Engineer (E-) finds test site (-LAB-) to address (-ORATE) (ELABORATE) complicated design (ELABORATE),
16 In Ulster (DOWN-), make a scene (-PLAY) (DOWNPLAY) or keep it discreet? (DOWNPLAY),
17 Old modes of transport (USED CARS), for Crusades (crusades) all over the place (= anagram indicator) (crusades = USED CARS),
19 In league with (ALLIED) boy released by Old Bailey (‘boy’ released by ‘Old Bailey’ = ldaile = ALLIED),
20 Street (ST-) in Waterford (-RING) (STRING) with a group of Arabians? (STRING of horses/Arabians),
23 Search (TRAWL) around (= reverse indicator) Lima (-L) for growth (wart = -TRAW) (TRAWL).