Retired cover girl in Catch-22 (7)
I believe the answer is:
dilemma
'catch-22' is the definition.
(catch-22 is a type of problem or dilemma)
'retired cover girl' is the wordplay.
I cannot really see how this works, but
'cover' could be 'lemma' (lemma is a kind of cover) and 'lemma' is present in the answer.
'girl' could be 'di' and 'di' is present in the answer.
No letters remain.
This explanation may well be incorrect...
'in' acts as a link.
Can you help me to learn more?
(Other definitions for dilemma that I've seen before include "Difficult-choice situation" , "Unpalatable choice" , "doubtful state" , "Difficult choice; quandary" , "I'm lamed - it's a puzzle" .)