Burn for wickedness with gruesome ends (5)
I believe the answer is:
singe
'burn' is the definition.
(singing is a kind of burning)
'wickedness with gruesome ends' is the wordplay.
'wickedness' becomes 'sin' ('sin' can be a synonym of 'wickedness').
'with' is a charade indicator (letters next to each other).
'ends' suggests removing the centre.
'gruesome' with its middle taken out is 'ge'.
'sin'+'ge'='SINGE'
'for' acts as a link.
(Other definitions for singe that I've seen before include "Effect of fire" , "Result of match accident" , "Burn slightly on surface" , "Scorch slightly on surface" , "Burn; ignes (anag.)" .)