Left murder victim's identification tag (5)
I believe the answer is:
label
'identification tag' is the definition.
(I've seen this before)
'left murder victim's' is the wordplay.
'left' becomes 'l' (common abbreviation).
'murder victim' becomes 'abel' (Biblical character).
'l'+'abel'='LABEL'
(Other definitions for label that I've seen before include "Put a name to" , "Tag or trade name" , "Designate" , "Identifying tag" , "Give name to" .)