Solution to 14A has been deliberately left unsolved and is to be answered only by a non-regular / novice commenter, with proper annotation. Those who have answered earlier in the week, please give others a chance.
Open for anyone to answer, if not solved by 1 PM.
ACROSS
1 Glow in arcade, perhaps (8) RADIANCE*
5 Number nine in standings at first in game (6) TENNIS {TEN}{Nine}{In}{St...s}
9 Over concerned with correctness, engineer cited a new paper at first (8) PEDANTIC {CITED+A+N+Pa..r}*
10 Astuteness of copper aboard - so be it (6) ACUMEN {A{CU}MEN}
12 Mimicry by primate on railway line (5) APERY {APE}{RY}
13 Awareness of king currently on narrow platform (9) KNOWLEDGE {K}{NOW}{LEDGE}
14 Story not essentially missing skill (6) ?A?E?T (Addendum - TALENT {TALE}{NoT} - See comments)
16 Tiredness of stout one regularly missing gluten (7) FATIGUE {FAT}{1}{GlUtEn}
19 Invalidate fully in new order (7) NULLIFY {FULLY+IN}*
21 Clergyman to heal without a hint of therapy (6) CURATE {CUR{A}{Th...y}E}
23 Not good working to conceal fortune - racket may be involved in this (9) BADMINTON {BAD}{MINT}{ON}
25 Doctor cutting tea for coffee (5) MOCHA {MO}{CHA} What's the role of cutting? (Addendum - {MO}{CHAi} - See comments}
26 Encroachment at home beside street (6) INROAD {IN}{ROAD}
27 First to last shoe splitting tumble in kicking game (8) FOOTBALL {F{(-b)OOT(+b)B}ALL}
28 It may be played by pawn easily losing heart (6) HOCKEY {HOCK}{Ea..lY}
29 Source of light on carrier - one that may fly through space (8) STARSHIP {STAR}{SHIP}
DOWN
1 Repeat broadcast of race outside Portugal (6) REPLAY {RE{P}LAY}
4 What an insect may play? (7) CRICKET [DD]
6 Crate also transported in device that moves up (9) ESCALATOR*
7 Part of piano made for one that keeps moving (5) NOMAD [T]
8 Star in retrospect embarrassed with editor, split away (8) SUNDERED {SUN}{RED<=}{ED}
11 Whip returned for sport (4) GOLF<=
15 Expel one minister in delight (9) ELIMINATE {EL{1}{MIN}ATE}
17 Charges a tenor in a bad way to enter a party uninvited (9) GATECRASH {CHARGES+A+T}*
18 Condescending aristocrat follows saint initially, braking is hard (8) SNOBBISH {NOB}<=>{S} and {Br...g}{IS}{H}
20 Mythical creature at this time on island (4) YETI {YET}{I}
21 Make up of criminal, firm on court (7) CONCOCT {CON}{CO}{CT}
22 Everyone amidst German operation to quickly make progress (6) GALLOP {ALL} in {G}{OP}
25 Doctor on small hill to move fast (5) MOTOR {MO}{TOR}
Reference List
New = N, Railway = RY, King = K, Doctor = MO, At home = IN, Portugal = P, Grand = G, Editor = ED, Minister = MIN, Tenor = T, Saint = S, Hard = H, Court = CT, German = G, Operation = OP