I took a little more than an hour to complete this puzzle which I would rate as ‘above-average’ in difficulty. My entering one or two wrong answers initially did not help matters. I got 4ac first and did not read any Down clue until I solved some 10 or 12 in the same set (this may be the reason for total time taken but fast filling-in is never my aim). The left vertical half proved to be difficult, more so the SW corner. The last to fall were 29ac and 24dn.
Across
1 ENSURE – (-c)ensure
10 TROUSSEAU – t,Rousseau
11 REPEL – rev. of ‘leper’
12 RUDE – (-p)rude
13 MINDREADER – min(dread)er
15 LAMPREY – lam, prey – This gave me a lot of trouble. ‘Buffet’ is a noun in surface reading but does a switcheroo as a verb in wordplay.
19 UNITED – un (‘a’ in French), ited* (anag. of ‘diet’)
21 PROPOSE – prop, (-h)os
23 ACQUAINTED – ac(quaint)e, d
25 RACE – r, ace (a second ace in succession!)
27 SWIFT – s(w.)ift
28 DECEPTIVE – dec(ep.)tive* (anag. of ‘evicted’) – Another clue that eluded me for a long while even though I knew the container, as deriving the abbr. ep. from ‘epistle’ (letter) involves some mental jousting.
29 MISPRINT – MI (abbr. of Military Intelligence)-sprint
30 STINGY – sting, y – To derive ‘sting’ from ‘upset’ we have to go to the outer reaches of our mind.
Down
2 SWORDSMAN – s.,wordsman – a rare, but legitimate, abbreviation for ‘succeeded’ and a seemingly new but actually very old term for a verbalist.
5 ECUADOR – anag. of ‘caroued’ after removing ‘s’ (‘old Bob’)
7 TEPID – te(pi)d, ‘pi’ being the mathematical term for “the ratio of the circumference to the diameter of a circle”.
21 PIERCE – pie(r.)ce – A third clue that took some thinking! I am not quite happy with the surface reading of the clue; I can understand someone filing a report but not ‘filling’ a ‘report’.
22 BALSAM – balsa, m
24 QUITS – When one says ‘quits’ one declares even with another. In wordplay I think there is deletion of ‘o’ from ‘quoits’ (game) but I am yet to see the full implication of ‘half-hearted’.
Sorry for bumping into myself! Re ‘half-hearted game’, the heart of ‘quoits’ is qu(OI)ts and half-hearted might be ‘o’. Still, I don’t see where the deletion indicator is.
Rishi, I think you have this absolutely right. Half-hearted is itself the deletion indicator. And as you point out OI is the heart of Quoits (whatever that is) so O is half the heart. You’ve done it.