Across:
1 Get rid of (DEPOSE) diamonds (D-) and ecstasy (-E-) for model (-POSE) (DEPOSE),
4 A (A-) way (-VIA-) into (into = -TION) production (= anagram indicator) (AVIATION) that’s bound to take off with a pilot (AVIATION),
9 Welsh (W-) leek (leek = EEKL-) soup (= anagram indicator) taken from back of quality (back of quality = -Y) (WEEKLY) magazine (WEEKLY),
10 University (U-) and institute (Dublin Institute of Technology = -DIT-) in need (-NE-ED) (UNEDITED) of a first draft perhaps (UNEDITED),
12 A really small amount (SCINTILLA) of lilac isn’t (lilac isn’t = SCINTILLA) problematic (= anagram indicator),
13 Course starting (course starting = C-) with exam (-ORAL exam) (CORAL) referring to what’s on reef (CORAL),
14 Deposits (DOWN PAYMENTS) from half of 1 down (half of “downside” = DOWN) on settlements (PAYMENTS) (DOWN PAYMENTS),
18 Opens 14 across (opens “down payments” = DOWN-) on container (-LOAD-) and is allowed to take (-ABLE) (DOWNLOADABLE) what can be shifted between the networks (DOWNLOADABLE),
21 Old (O-) wrestling (= anagram indicator) game (game = -MEGA) (OMEGA) was the end of the line for the Greeks (final Greek letter = OMEGA),
22 Dance (CONGA) director (D-) is drunk (-RUM) (CONGA DRUM) and gets played by musician (CONGA DRUM),
24 Moving (= anagram indicator) camera (camera = MA-ACRE) captures old police force (-SS-) (MASSACRE) in Night of the Long Knives (Hitler’s June 1934 MASSACRE of the Brownshirts),
25 Traditionalist (purist) loses the head (p) (“purist” without “p” = -URIST) after (= positional indicator) Jack (J-) (JURIST) lays down the law (JURIST),
26 Big (LARGE-) ship (-SS-) linked to oriental (east = -E) (LARGESSE) charity (LARGESSE),
27 Sara takes off in relay races (“Sara” takes off in/leaves “relay races” = relyce = CELERY) with green stick (CELERY),
Down:
1 Negative aspect (DOWNSIDE) of Ulster team (DOWN-) on border (-SIDE) (DOWNSIDE),
2 Early observations (PREVIEWS) of post (P-) and criticism (-REVIEW-) linked to school (-S) (PREVIEWS),
3 Breakup (SPLIT) of the former Yugoslavia (SPLIT),
5 Provides a good view (VANTAGE POINT) of Bill (ad) leaving benefit (advantage) (“ad” leaving “advantage” = VANTAGE) for Spike (spike = POINT) (VANTAGE POINT),
6 A (A-) detective (-DI-) finding kitty (-CAT-) buried in plot (B-ED) (ABDICATED) gave up power (ABDICATED),
7 Rent in (rent in = INTERN) doubt (= anagram indicator) for The Apprentice (INTERN),
8 Signal (NOD-) from university (University of Limerick = -UL-) is key (music key = -E) (NODULE) – if it gets more voluminous, one might have to have it out with the doctor (NODULE),
11 What the comic actors are doing (PLAYING CARDS) in The Pack (PLAYING CARDS),
15 Reproduce (PROPAGATE) theatrical accessory (PROP-) for a (-A-) theatre (-GATE Theatre) (PROPAGATE),
16 Failed (ABORTIVE) to halt (ABORT-) those in the middle of the river (those in the middle of the “river” = -IVE) (ABORTIVE),
17 Rewrite (= anagram indicator) grey tome (grey tome = GEOMETRY) for maths class (GEOMETRY),
19 Conventional type (FORMAL) of wild (= anagram indicator) flora (flora = FOR-AL) around motorway (-M-) (FORMAL),
20 Won’t hear a bad word said against anyone on screen (CENSOR) and is bound to clean up (CENSOR),
23 Keen (ACUTE) for a (A-) cut (-CUT-) at flyweight at the centre (“flyweight” at the centre = -E) (ACUTE).