Opera socially acceptable in Lent for example (5)
I believe the answer is:
faust
'opera' is the definition.
(I've seen this before)
'socially acceptable in lent for example' is the wordplay.
'socially acceptable' becomes 'U' (as in U and non-U language).
'in' is an insertion indicator.
'lent for example' becomes 'fast' (I can't explain this - if you can you should believe this answer much more).
'u' going inside 'fast' is 'FAUST'.
Can you help me to learn more?
(Other definitions for faust that I've seen before include "Opera" , "1 28 [EPIC POEM]" , "Goethe play" , "Literary scholar" , "Alchemist" .)