Full opera needs cutting down for run (4)
I believe the answer is:
lope
'for run' is the definition.
(lope is a kind of run)
'full opera needs cutting down' is the wordplay.
'needs cutting down' says the answer is hidden in the clue (some letters must be cut from around the answer).
'LOPE' is hidden in the letters of 'full opera'.
(Other definitions for lope that I've seen before include "Slow pace" , "Canter" , "Stride along" , "Run along easily" , "Run slowly with pole" .)