Thanks for the replies.
rusty, I hadn't considered 'invert', though I've heard the term. I can't see how it works exactly beyond it meaning 'turn up', but maybe that's it.
The thing is, why use 'poof'? Seems dodgy to me.
mamya, the crude meaning(s) crossed my mind too, but, without being indelicate, they could just as well apply to straights as well. Where are the red-faced smiley emoticons when you need them?
Perhaps I should change the subject, because I can't parse 13A Offal either!
Tripe à la Provençale here must be eaten to be approved (5) O-F-L
I can see tripe as the def, but that's it.