Blacken on the grill (4)
I believe the answer is:
char
'blacken on the grill' is the definition.
(I've seen this in another clue)
This is the entire clue.
(Other definitions for char that I've seen before include "Partially burn; fish" , "Scorch: trout-like fish" , "Brown" , "Cleaner - tea" , "clean > burn" .)