Once again only a few, that I can't see.
6d Game with poor player (6) R - B - I - RABBIT? Why?
18a Usually is beaten hollow (4) D - U - DRUM?
27a Concluded most of the series caused discomfiture (9) O - E - T - R - W OVERTHREW? OVERTHROW, wrong tense.
All help appreciated.
Chambers gives 'rew' as a Spenserian variant of 'row'. So there's an argument to be made for both answers (though I suspect overthrow is more likely, because this is the ST regular cryptic, not Mephisto)