Abraham Lincoln, initially, was a murder victim (4)
I believe the answer is:
abel
'a murder victim' is the definition.
(Biblical character)
'abraham lincoln initially' is the wordplay.
'abraham' becomes 'abe'.
'initially' indicates taking the first letters.
The first letter of 'lincoln' is 'l'.
'abe'+'l'='ABEL'
'was' acts as a link.
(Other definitions for abel that I've seen before include "Old Testament brother" , "Cain's victim; - Magwitch (Great Expectations)" , "one killed early" , "Brother killed by Cain" , "character in the Bible" .)