Scorch a fish (4)
I believe the answer is:
char
This clue is a double definition.
'scorch' is the first definition.
(I know that scorch can be written as char)
'a fish' is the second definition.
(char is a kind of fish)
(Other definitions for char that I've seen before include "Perhaps overheat" , "Tea (sl.)" , "Become black by burning" , "Singe, scorch" , "Fish < tea" .)