Solution to 10A 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 He, maybe sprinkled salt first, then a bit of pepper just in time (4-4) LAST GASP {GAS}<=>{SALT*} then {Pe...r}
5 Sound of wind passing from southern tip of fellow, next to a pair of orbs, quietly (6) SWOOSH {S}{f...oW}{OO}{SH}
9 Hate Fortran course contents (7) RANCOUR [T]
10 Welcome computer cycles in the greatest lab, up front (3,4) A?L ?A?L ()
11 Projection: ex-U.S. president not running (5) CLINT CLINTon
12 Family is caught in deficits — any disbursements under review? (8) DYNASTIC [T<=]
13 Lecture confused Mr. Sen about love (6) SERMON {MR+SEN}* over {0}
14 Courier perhaps returned letters from inoperative Cafe Pythagoras (8) TYPEFACE [T<=]
18 Might work — he's starting off novel AIs! (8) STRENGTH {HES+sTaRTiNG}*
20 Grand, completely naked neighbour's sexy without shirt (6) HEROIC {n..gHb..r}{EROtIC}
23 Proposal of monarch bearing love? It's rejected in favour of second Earl (8) QUESTION {QUE{-e+its<=)STI{O}N}
25 Grab rail, no support in vessel! (5) GRAIL {GRAb+raIL}
27 Every now and then, Sheela did jump over small pools of water (7) PUDDLES {ShEeLa+DiD+jUmP}<=
28 New and old blending in coastal city's craft (7) GONDOLA {GO{N+OLD}*A} GOA is not a city but a State
29 Some grammar tyrants persecuted good man (6) MARTYR [T]
30 Vehicle is back — they finally fixed lube and paint (4,4) NAVY BLUE {VAN}{theY}{LUBE*}
DOWN
1 They write songs in registers that captivate; I cry, moved (9) LYRICISTS {L{I+CRY}*ISTS}
2 Regularly spurn engineer with brighter outlook (7) SUNNIER {SpUrN+eNgInEeR}
3 Good crowd thronged at first, now unfortunately no one is here any more (5,4) GHOST TOWN {G}{HOST}{Th...d}{NOW*}
4 Take steps — rubbish lying around in corner (6) STRIDE {S{DIRT<=}E}
6 Wife makes speech lacking a hint of truth and rambles (5) WALKS {W}{tALKS}
7 No car in America features this instrument (7) OCARINA [T]
10 A racket, as they say, is irritating (6) ANNOYS {A}{(~noise)NNOYS}
15 Join forces with dunces, essentially, during extremely, extremely desperate situation (9) EMERGENCY {MERGE}{duNCes} in {Em...cY}
16 By cracking cryptic clue, head gets clear (9) EXCULPATE {E{X}CUL*}{PATE}
17 Top places for jerks (6) ATTICS {AT}{TICS}
19 More like a balloon going up or down (7) ROUNDER [DD]
21 Very successful top students' list announced (2,1,4) ON A ROLL (~ honour roll)
22 Heart going out for top cop behind clearing mystery (6) ENIGMA {EN(-e+IG)IGMA}
24 Reckless apprentice shadowing Gussalufz in secret (5) SILLY {S{I}{L}LY}
26 One second ... (deleted jerk's unwelcome message) (4) SPAM SPAsM
Reference List
Southern = S, Quietly = SH, Shirt = T, Support = BRA, New = N, Good = G, Corner = SE, Wife = W, Husband = H, By = X, Apprentice = L, Second = S