Obviously, I need to look again at my 17 D and 25D (not fully parsed). Surely Madam works in 21A doesn't it, Chrise? For 1 A and 1a think chess piece and anagram of last letters respectively.
I parsed 1a as follows:
first 3 letters (away's first)
4th letter (abbreviation for large)
last 3 letters (chess piece minus r for king: I assume that the dash sign is the minus indicator.