Burn black, sear (4)
I believe the answer is:
char
I believe this is a double definition.
'burn black' is the first definition.
(I've seen this in another clue)
'sear' is the second definition.
(I know that sear can be written as char)
(Other definitions for char that I've seen before include "Drink" , "Scorch - fish - cleaning lady" , "Overcook - fish - daily" , "Make black by burning, say toast" , "'Mrs Mopp'" .)