Live piece started (5)
I believe the answer is:
begun
'started' is the definition.
(to start is to begin)
'live piece' is the wordplay.
'live' becomes 'be' (synonyms).
'piece' becomes 'gun' (slang term for a gun).
'be'+'gun'='BEGUN'
(Other definitions for begun that I've seen before include "Commenced" , "(Has) started" , "Opened" .)