Dandy consuming large turkey (4)
I believe the answer is:
'turkey' is the definition.
'dandy consuming large' is the wordplay.
'dandy' becomes 'fop' ('fop' can be a synonym of 'dandy').
'consuming' is an insertion indicator.
'large' becomes 'l'.
'fop' placed around 'l' is 'FLOP'.
(Other definitions for flop that I've seen before include "turkey" , "Failure - loll" , "Fall limply - box-office failure" , "crash" , "Total failure; fall heavily" .)