Gang leader burying extremely brave murder victim (4)
I believe the answer is:
abel
'murder victim' is the definition.
(Biblical character)
'gang leader burying extremely brave' is the wordplay.
'gang leader' becomes 'al' (Al Capone).
'burying' is an insertion indicator.
'extremely' says to hollow out the word (remove centre letters).
'brave' with its centre removed is 'be'.
'al' placed around 'be' is 'ABEL'.
(Other definitions for abel that I've seen before include "Old Testament brother" , "done in before anyone else" , "Cain's murdered brother" , "one killed early" , "One of the first children" .)