Cut when Chopin drops in (4)
I believe the answer is:
chop
'cut' is the definition.
(I know that chop is a type of cut)
'chopin drops in' is the wordplay.
'drops' suggests deleting specific letters.
'chopin' with 'in' removed is 'CHOP'.
'when' is the link.
(Other definitions for chop that I've seen before include "Use a cleaver" , "Cutting blow" , "Chinese seal" , "Dissect" , "Karate punch" .)