Whizzed through all of this but one has eluded me since Saturday - I’m guessing my final missing letter is ‘I’ in 31 across - but I have no idea why that would be a suitable answer.
I assume that's an 'i' rather than an 'l'. If so that's right. The i is missing from the word play as it's part of the hint. With the i, it's an old word for a pheasant's brood.