Lost leader held by state for murder (4)
I believe the answer is:
slay
'for murder' is the definition.
(synonyms)
'lost leader held by state' is the wordplay.
'leader' says to take the initial letters.
'held by' indicates putting letters inside.
'state' becomes 'say' (to state something is to say it).
The first letter of 'lost' is 'l'.
'l' put within 'say' is 'SLAY'.
(Other definitions for slay that I've seen before include "Kill intentionally" , "Destroy" , "Kill (literary)" , "Kill with premeditation" , "Kill, murder" .)