Burn (4)
'burn' is the definition.
(sear can mean to burn)
This is all the clue.
(Other definitions for sear that I've seen before include "Dried up, parched" , "Withered" , "Cook (quickly at great heat)" , "Burn briefly" , "Cauterise" .)
'burn' is the definition.
(charring is a kind of burning)
This is the entire clue.
(Other definitions for char that I've seen before include "way to make carbon" , "tea > daily" , "House cleaner" , "Perhaps overheat" , "Singe; a fish" .)
'burn' is the definition.
(synonyms)
This is the entire clue.
(Another definition for combust that I've seen is " Burn".)