Chap's giggling -- this could make one corpse (12)
I believe the answer is:
manslaughter
'this could make one corpse' is the definition.
(killing somebody)
'chap's giggling' is the wordplay.
'chap's' becomes 'man's' (chap can mean a man).
'giggling' becomes 'laughter'.
'mans'+'laughter'='MANSLAUGHTER'
(Other definitions for manslaughter that I've seen before include "charge?" , "Crime of killing, short of murder" , "slaying" , "Unlawful killing" , "Crime of unpremeditated killing" .)