Reduce to ashes (7)
I believe the answer is:
cremate
'reduce to ashes' is the definition.
(synonyms)
This is all the clue.
(Other definitions for cremate that I've seen before include "Burn a corpse to ashes" , "Have a burn-up" , "Burn a body to ashes" , "Burn (a dead body)" , "Destroy body by burning" .)