What scoffers do behind theatre screen again? (6)
I believe the answer is:
repeat
'screen again?' is the definition.
'what scoffers do behind theatre' is the wordplay.
'what scoffers do' becomes 'eat'.
'behind' means one lot of letters go next to another.
'theatre' becomes 'rep' (I've seen this in other clues).
'eat' after 'rep' is 'REPEAT'.
(Other definitions for repeat that I've seen before include "Parrot" , "Reiterate" , "Say again, echo" , "Say again, or belch (6" , "Quote from memory" .)