A little harder than usual from Quixote, I found. Solving time, 31 mins.
Notes on some clues below – happy to explain others if asked.
ACROSS
6 S (last letter of chips) CUP Was looking for ‘cha’ for a while.
14 IRREGULAR VERBS As ‘do’ and ‘have’ are – good.
25 GO B A (NANA) S Gob = spit, as = when, nana = granny
DOWN
5 RASPBERRY Double definition
7 COULOMB “Charge physicist” The unit of charge, named after the physicist – a little surprised that the two parts of the clue were not more distinct. Or, maybe, a cryptic definition is intended, though then I thought there would have been a “?”
20 PAST Y i.e. at the end of the dictionary (under Z)
21 D (WEE) B Db = decibel (bit of noise)