Wind up gun lacking force (4)
I believe the answer is:
rile
'wind up' is the definition.
(I've seen this in another clue)
'gun lacking force' is the wordplay.
'gun' becomes 'rifle' (rifle is a kind of gun).
'lacking' suggests deleting specific letters.
'force' becomes 'F' (symbol used in Physics e.g. f=ma).
'rifle' with 'f' taken out is 'RILE'.
(Other definitions for rile that I've seen before include "Bother" , "Make angry" , "Exasperate" , "Provoke" , "Irk" .)