A tad puzzled by a couple of parsings, help appreciated...
20a - I assume the first 3 letters are from "captive enemy" but how do we get the last 2?
29d - I get the "back garden" but e why " where to hang sheets"? I did wonder if the definition might be just "garden" and that "back" could be a reversal indicator but, having looked up the answer in reverse, that doesn't seem likely.