An excellent and chewy puzzle to ring in a new month with, I thought. My aged mum is staying with us for the Easter hols to perform important kid-wrangling duties, so the Blogging Room was out of bounds this morning, meaning I had to do the puzzle recumbent in bed this morning on an unfamiliar laptop; in such circumstances I was okay with coming in inside the quarter-hour. It seems from the Club forum that there may be an alternative plausible answer to 27ac that laid a number of solvers low, so I'm surprised and delighted that I didn't fall into that trap, as it seems like the kind of thing I'd normally do unerringly, and I have no idea what a SEAMARK is when it's at home.
Doubleplusgood economy of cluing on display here (though that may result in a couple of the anagrams being just too simple for some tastes, I don't know) and some truly great surfaces: 5dn's splendidness was a little muddied by the fact that I've spent a lot of time since mulling over in which senses the Holy See is a court, though I expect it is totally legit. No such qualms with 1D, my LOI (I thought of the right answer and most of the right lines early, but I was looking for a DEPPA or such!) and COD. 18ac gave me some pause but it's just one of those lovely English words that means both itself and the opposite of itself, isn't it? I did find 28ac slightly on the laborious side, unless I've parsed it incorrectly of course, and some of the clues were a little stomach-turning for a mostly-vegan like myself, but these are minor eggs and cream for a crossword that on the whole was thoroughly top-notch. All glory, laud and honour to the setter!
| Across |
| 1 | PLANCK - physicist: LAN{e} ["short" course] in PC K [computer | K{nowledge} "just beginning"] |
| 4 | CHEMISTS - drug dealers: CHE MISTS [guerilla leader | films] |
| 10 | NOURISH - supply with food: {s->N}OURISH [like grapefruit, "with different starter"] |
| 11 | LAYETTE - first gear: L [learner] + YET [still], ATE [worried] about that |
| 12 | ANTI - opponent: {c}A{n}N{o}T {w}I{n} "being regularly eliminated" |
| 13 | DISSONANCE - lack of harmony: IS SON [is | issue] in DANCE [part of ballet] |
| 15 | TAIWANESE - Chinese: T.A. [army] + WANES [loses dominance] in {or}IE{nt} ["central parts of"...] |
| 16 | AT SEA - lost: about S ["start of" S{eason}], A-TEA{m} [top side "almost"] |
| 18 | LIEGE - subject: {coll}EGE IL{logically} ["suffering cuts" ... "put back"] |
| 19 | BRASSERIE - restaurant: ASSER{t} [say, "cut"] (that) BRIE [cheese] sandwiches |
| 21 | GRANT-IN-AID - financial assistance: (A GRAND I*) ["collected"] must include TIN [money] |
| 23 | SNAP - break: reverse of PANS ["placed the wrong way", slates] |
| 26 | NITPICK - carp: NIT [egg] served with PICK [cream] |
| 27 | SEAMARK - something observable in the water: SEAM ARK [join | sailing vessel] |
| 28 | CAR PARKS - lots there (i.e. in the US): ARK [US state] going into CARP S [fish | {busines}S "ultimately"] |
| 29 | STOREY - floor: Y [year] on STORE [shop] |
| Down |
| 1 | PANDA - creature: reverse of {h}AD NAP [slept "upside down", "head tucked away"] |
| 2 | AQUITAINE - French region: A QUIT A IN E [a | desert | area | in | eastern] |
| 3 | CAIN - murderer: homophone of CANE ["mentioned" form of punishment] |
| 5 | HOLY SEE - court: L{ad}Y ["case of"...] entering HOSE [tube] + E{arl's} ["heading for"...] |
| 6 | MAYONNAISE - sauce: YO{u} ["briefly"] tucked into MANNA [heavenly food] + I'S [one's] served with {chees}E ["last of"...] |
| 7 | SET ON - attack: (STONE*) ["thrown"] |
| 8 | STEVENAGE - Hertfordshire town: reverse of VETS [checks "up"] on {m}ENAGE [household, "miles away"] |
| 9 | SHRIKE - songbird: (HIKERS*) ["disturbed"] |
| 14 | PALESTRINA - composer: PALEST [most unimpressive] + RIN{g} [opera cycle "left incomplete"] by A |
| 15 | TELEGENIC - worth watching: E.G. [for example] during (ELECTI{o}N*) ["broadcast", "nothing standing out"] |
| 17 | STRANRAER - Scottish port: reverse of REAR N ARTS [back | new | cultural activities "set up"] |
| 19 | BANGKOK - city: BANK OK [financial institution | agreed] to accept G [grand] |
| 20 | AMIDST - in the middle of: A.M. [the morning] + ID {e}ST [i.e. "when energy is fading"] |
| 22 | ASTIR - not still: ASTI R [sparkling wine | right] |
| 24 | POKEY - having little room for manoeuvre: KEY [chief], (with) P.O. [petty officer] initially |
| 25 | PAST - bygone days: PA'S T [old man has | "little" time] |