Across:
1 A (A-) verbose leader (‘Verbose’ leader = -V-) from The Journal (diary) needs no introduction (d) (‘diary’ without ‘d’ = -IARY) (AVIARY), as it’s for the birds (AVIARY),
4 Independent (I-) to take a seat (sit = -T IS) rejecting (= reversal indicator) some initial (‘Some’ initial = S-) help (-AID) (IT IS SAID), or so the story goes (IT IS SAID),
9 View (ASPECT) of a (A-) small (-S-) leaderless (o) bunch of oil producers (‘OPEC’ without ‘o’= -PEC-) from half of Texas? (Texas = TX + half of ‘TX’ = -T) (ASPECT),
10 Clip of (t) the funny business (‘skit’ without ‘t’ = SKI) by the Irish and English (RACES) (SKI RACES) witnessed at the Olympic Games (SKI RACES),
12 Sets up (= reversal indicator) storage facility (silo = -OLIS) for most of (k) the meat (‘pork’ without ‘k’ = por = -ROP-) from California (CA = AC-) (ACROPOLIS) by an old citadel (ACROPOLIS),
13 Beastly type (TAPIR) of prey from Tipperary (‘prey’ from ‘Tipperary’ = tipar = TAPIR),
14 The Buick stops here presumably (Buick car stops at TRAFFIC LIGHT) for Amber (TRAFFIC LIGHT),
18 They have a reputation for sizing up what’s in 20 down (TAPE MEASURES sizing up ‘metric’) for judge (-MEASURE-) in recordings (TAPE -S) (TAPE MEASURES),
21 Scrounger (LEECH) on the back foot (heel = LEE-H) over returning (= reversal indicator) conservative (-C-) (LEECH),
22 It’s not quite true that (OFF-CENTRE) this is the end of 5 down (end of ‘takes time off’ = OFF) – have heart? (-CENTRE) (OFF-CENTRE),
24 Material (CORDUROY) is cut for delivery (umbilical CORD-) to your (your = -UROY) building (= anagram indicator) (CORDUROY),
25 European resident (Serb = S-ERB) admits a wake (awake = -UP-) (SUPERB) is awe-inspiring (SUPERB),
26 Basic Sky (basic sky) package (= anagram indicator) (basic sky = SICKBAYS) found in most hospitals? (SICKBAYS),
27 Temporary occupant (LESSEE) of port (port/left = L-) city in Germany (Essen) hasn’t finished (n) (‘Essen’ without ‘n’ = -ESSE-) engineering (-E) (LESSEE).
Down:
1 A (A) complex (= anagram indicator) claret (claret = LA C-RTE) – round, initially aromatic (initially ‘Aromatic’ = -A-) (A LA CARTE) and can be ordered separately from the menu (A LA CARTE),
2 Like Caesar (like Caesar = IMPERIAL) in August? (IMPERIAL),
3 State once again (RECAP) takes rap (R-AP) covering up ecstasy (-E-) at college (-C-) (RECAP),
5 Film units (TAKES) use a stopwatch (TIME) that’s not accurate (OFF) (TAKES TIME OFF) and stops temporarily (TAKES TIME OFF),
6 Reaches out (STRETCHES) to those in The Joy (prison terms = STRETCHES),
7 Don’t object to (ACCEPT) performance (AC-T) covering Coldplay’s first (‘Coldplays’ first = -C-) record (Extended-Play record = -EP-) (ACCEPT),
8 Rested (rested = DESERT) awkwardly (= anagram indicator) in ditch (ditch/abandon = DESERT),
11 A spot of moonlighting perhaps (BLACK ECONOMY) for those selling illegal cigarettes (BLACK ECONOMY),
15 Foreign leader (‘Foreign’ leader = F-) and whip (-LASH) in the plot (-BULB) (FLASHBULB) employed by one of those old ones possible taking a shot in the dark (FLASHBULB employed by old camera in the dark),
16 Gets under one’s skin (annoys/bothers = B-OTHERS) reading (-R-) inside (BROTHERS) to the siblings (BROTHERS),
17 Labs seem (labs seem = ASSEMBLE) uncomplicated (= anagram indicator) to construct (ASSEMBLE),
19 Bars (bars/obstructs = BLOCKS) for British (B-) rugby players (-LOCKS) (BLOCKS),
20 It’s a measure (METRIC) of the two police forces, one new (MET), one old (RIC), on neighbouring islands (MET + RIC= METRIC),
23 It’ll come out (EXUDE), old partner (EX-) is due (due = -UDE) treatment (= anagram indicator) (EXUDE).