Across:
1 Season (spring) isn't finished (g) ('spring' without 'g' = SPRIN-) for first team (first 'Team' = -T) (SPRINT) in Rush (rush = SPRINT),
4 Anonymous (A-) police department (Criminal Investigation Department = -CID) experiment (TEST) (ACID TEST) will conclusively tell you everything you need to know (ACID TEST),
9 Musical interval (OCTAVE) is sinister coming from service station (‘sinister’ coming from ‘service station’ = evctao = OCTAVE),
10 Sounds like (= homophone indicator) an instruction to find that woman (‘go get her’ = ‘GO-GETTER’), the kind that’s ambitious (GO-GETTER),
12 Shouts from the rooftops (PROCLAIMS): “Pressure (P-) on Carlos (Carlos) Cook (= anagram indicator) (Carlos = -ROCLA-S) taking in back (= reverse indicator) road (MI = -IM-)” (PROCLAIMS),
13 Mam and Dad (MATES) closing 18 across (closing ‘running mates’ = MATES)?
14 Irish love (Irish ‘love’ = grá = GRA-) Greek character (21st letter of Greek alphabet = phi = -PHI-) from top-class (top ‘Class’ = -C), ground-breaking (NOVEL) (GRAPHIC NOVEL) comic story (GRAPHIC NOVEL),
18 Part of the ticket (RUNNING MATES) for taking flight (RUNNING) with partners (MATES) (RUNNING MATES),
21 Keen (ACUTE) for a (A-) piece of the action (-CUT-) at the end of June (end of ‘junE’ = -E) (ACUTE),
22 For example, the English (EUROPEANS) capital (EURO-) and park (-P-), for Cezanne even (‘cEzAnNe even letters = -EAN-), is small (-S)? (EUROPEANS),
24 Crab (female crab = HEN) finds Labour (Labour PARTY) (HEN PARTY) is no place for the men (HEN PARTY),
25 Get twisted (TANGLE) on cocktails at The Centre (‘cockTails’ at the centre = T-) with cast (cast/fish = -ANGLE) (TANGLE),
26 Reads one’s fortune in tealeaves, for instance (PORTENDS), or wine (PORT-) dregs (-ENDS) (PORTENDS),
27 Hidden (SECRET) on top of cambium (on top of ‘Cambium’ = -C-) in wild (= anagram indicator) trees (trees = SE-RET) (SECRET).
Down:
1 Old (O-) priest (-PP-) taken in by engineer (stage = ST-AGE) (STOPPAGE) – and those in The Union sanctioned it? (STOPPAGE),
2 What’s the logic (RATIONAL) in thinking (rationale) endlessly (e)? (‘rationale’ without ‘e’= RATIONAL),
3 It is missing from violent (‘it’ is missing from ‘violent’ = volen = NOVEL) piece of fiction (NOVEL),
5 Race (CROSS-COUNTRY race) of angry (CROSS-) people (-COUNTRY) (CROSS -COUNTRY),
6 Fantasy football side (DREAM TEAM) in bedtime story perhaps (DREAM) for playgroup? (play group = TEAM) (DREAM TEAM),
7 Concerns Will (concerns will / ESTATE) and sweetheart (‘swEet’ heart = E-) from New York (-STATE) (ESTATE),
8 Starting from here (starting from ‘Here’ = -H-) in confidence (trust = T-RUST) (THRUST) or that’s the gist (THRUST),
11 Cut (c) record (disc) (‘disc’ without ‘c’ = DIS-) for couple (-CONNECT-) with energy (-E-) that’s top drawer (top ‘Drawer’ = -D) (DISCONNECTED) and unplugged (DISCONNECTED),
15 Hard (H-) at The Centre not (the centre of ‘nOt’ = -O-) to take advantage of (-USE-) partner (-MATE) (HOUSEMATE) – the one who shares (HOUSEMATE),
16 Ill at ease (STRANGE-) with writing (from the 3Rs = -R) (STRANGER) in The Outsider (STRANGER),
17 In the beginning (‘In’ the beginning = I) taken in by easiest (easiest) problem (= anagram indicator) (easiest = AS SEE IT) (AS I SEE IT), in my view (AS I SEE IT),
19 White (W-) snake (asp = -AS- -P) concealing unpleasant smell (hum) briefly (m) (‘hum’ without ‘m’= -H U-) (WASH UP) gets to drift onto the beach (drift onto the beach = WASH UP),
20 Athlete (RUNNER) found up (= reverse indicator) in Burren nursing home (found up in ‘burREN NURsing home’ = rennur = RUNNER),
23 Parking (P-) on narrow street (-LANE) (PLANE) is bound to take off (PLANE).