Solution to 1A 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.
ACROSS
1 One always fresh and smart (6) S?R?C? (Addendum - SPRUCE [DD] - See comments)
11 So hot again…removing shorts, stripped completely (5) HENCE {H}ENCE Anno pending (Addendum - {HE}{ENCorE} - See comments)
12 Last-minute changes to make ATM device (7) UTENSIL {+ATM = LAST MINUTE} [CA]
13 Graceful angel is so merciful at heart (7) LISSOME [T]
14 More time to pack ten tonnes (5) EXTRA {E{X}{T}RA}
15 Routine starting to debug anomalous Y-O-Y data (3-2-3) DAY-TO-DAY {De..g}{Y-O-Y+DATA}
18 Short article about unfinished, cryptic, enigmatic painting (8) TRIPTYCH {T{CRYPTIc*}He}
20 Host KrisKross returns to make an observation to the audience (5) EMCEE {ME<=}{~ see CEE}
23 Successful company - one contracting wheat possibly (7) UNICORN {UNIt}{CORN}
25 Unwanted, nonstop jabbers? (7) NEEDLES NEEDLESs
26 Lived in degenerate retro bar (5) DWELT {LEWD<=}{T}
27 Laurel, say, always leading comic genre (9) EVERGREEN {EVER}{GENRE*}
28 Law has reviewed evidence in handbag (8) RETICULE {R{CITE<=}ULE}
29 Commands boy to leave frontiers (6) ORDERS bORDERS
DOWN
1 Enjoyed preserved painting belonging to you and me (8) SAVOURED {SAV{OUR}ED}
2 Most foul smell, primarily in dirty tanker (7) RANKEST {RANKE{Sm..l}T*}
3 Cheat using comedian's instrument (4,5) CARD SHARP {CARDS}{HARP}
5 Untrue, stale story by subordinate to win praise that should be mine (5,2,7) STEAL MY THUNDER {STALE*}{MYTH}{UNDER}
6 Losing final seconds in a game is painful (5) ACHES {A}{CHESs}
7 A long, lively party inside boat (7) GONDOLA {A+LONG}* over {DO}
8 Not those Sunday papers (6) THESES {THESE}{S}
9 Polluted Delhi can really do without pure air? Eventually, it's unlikely to happen (1,4,3,2,4) A COLD DAY IN HELL {DELHI+CAN+reALLY+DO}*
16 Go around cycling? Agree excitedly, being very enthusiastic (9) OVEREAGER {(-r)OVE(+r)R}{AGREE*}
17 Space organization involved in action, uplifting farmers (8) PEASANTS {ST{NASA}EP}<=
19 Plan to wear torn dress (7) RAIMENT {R{AIM}ENT}
21 Old king having support for educational institution (7) COLLEGE {COL{LEG}E}
22 Star very angry about part (6) SUNDER {SUN}{RED<=}
24 Choose one ultimately classic visual (5) OPTIC {OPT}{1}{c...iC}
Reference List
Key = ESC, Tonnes = T, Bar = T, Boy = B, Sunday = S






