Scorch, cauterise (4)
I believe the answer is:
sear
This clue is a double definition.
'scorch' is the first definition.
(I know that scorch can be written as sear)
'cauterise' is the second definition.
(I've seen this before)
(Other definitions for sear that I've seen before include "Cauterize" , "Burn briefly" , "Scorch, brand" , "Make very hot and dry" , "Scorch or burn the surface of" .)