Thanks for the explanation, listenup. I, too, was stumped by that clue. I think it's the only one that I didn't manage to parse.
I think it's a poor clue. The first part of the answer is in the idiomatic phrase which forms the basis of the wordplay. I regard that as poor cluing practice unless there is a very witty reason for doing so. To add to the confusion, the four-letter word in the answer means 'lose it' on its own, so the solver naturally struggles to see how the last four words of the clue lead to the second word.