ACROSS
1 Give fruit salad right away to refugee (8) FUGITIVE {GIVE+FrUIT}*
5 Billion accepted in banknotes for castle in N. African town (6) CASBAH {CAS{B}{A}H} Accepted/A? It's there in Chambers dictionary
10 Time to accumulate runs with bit of ease in match (5) AGREE {AG{R}E}{Ease}
11 Emission percentage cut by revolutionary contribution (9) RADIATION {RA{AID<=}TION}
12 Cackling back, gigantic creature grabs raptor's head (9) GIBBERING {BIG<=}{BE{Ra...r}ING}
13 What baby wears to sleep extremely peacefully? (5) NAPPY {NAP}{Pe...lY}
14 Shudder as criminal finally enters court (6) BLENCH {B{c...aL}ENCH}
15 Old boy starting to turn impolite and impose in an unwelcome way (7) OBTRUDE {OB}{Turn}{RUDE}
18 Fantastic bistro alongside lake in English city (7) BRISTOL {BISTRO*}{L}
20 Owing money, one criminal returns to smuggle heroin at Cambodia (2,4) IN HOCK {1}{CO{H}N<=}{K}
22 Right after sacrificing rook, captures queen resulting in mate (5) EQUAL {rE{QU}AL}
24 Composed a nice tune, say (9) ENUNCIATE*
25 I hear vicar went berserk, scoring ecstasy in noisy mock serenade (9) CHARIVARI {I+HeAR+VICAR}*
26 Yellowish-green colour, a little garish for large pointed arch (5) OGIVE O(-l+g)GIVE
28 Revelations by meek gal as rogue wants money (8) LEAKAGES {mEEK+GAL+AS}*
DOWN
1 Fine footpath having good raised edge (6) FLANGE {F}{LAN{G}E}
2 Briefly return to pick up racy loose blouse (9) GARIBALDI {GA{RIBALD}In}
4 Leave rupees inside coat (7) VARNISH {VA{R}NISH}
6 Acting with haste, hit and bolt as fast as possible (7,3,5) AGAINST THE CLOCK {ACTING+HASTE}*{LOCK}
7 Airship starting to malfunction in unforeseen irregularity (5) BLIMP {BLI{Ma...n}P}
8 Sharpen tip of dagger to pierce tree for sugary secretion (8) HONEYDEW {HONE}{Y{Da...r}EW}
9 A cheat ensnaring American girl on island slowly (6) ADAGIO {A}{D{A}{G}{I}O}
16 Applying packs, treat acne that's persistent (9) UNCEASING {U{ACNE*}SING}
17 Releases repressed emotions in seedy cabarets (8) ABREACTS*
19 Lodge has small revolting room (6) LEEWAY {L{WEE<=}AY}
20 One maniac at store kills fellow - pointless (7) INUTILE {1}{NUT}{fILE}
21 Warns comrade tersely to hide (6) DETERS [T]
23 University teacher's rule (5) USAGE {U}{SAGE}
Reference List
Right = R, Billion = B, Accepted = A, Runs = R, Old boy = OB, Lake = L, Herion = H, Cambodia = K(Kampuchea), Rook = R, Queen = QU, Ecstasy = E, Large = L, Money = M, Fine = F, Good = G, RACY = RIBALD, Rupees = R, Cheat = DO, American = A, Girl = G, Fellow = F, University = U