Youngster buries dead corpse (4)
I believe the answer is:
body
'corpse' is the definition.
(thesaurus)
'youngster buries dead' is the wordplay.
'youngster' becomes 'boy' (**).
'buries' is an insertion indicator.
'dead' becomes 'd'.
'boy' enclosing 'd' is 'BODY'.
(Other definitions for body that I've seen before include "Substance" , "One-piece undergarment for women, covering the torso" , "Group of persons thought of as an entity" , "Person - corporation" , "Corpse; full quality of wine" .)