Make black tea (4)
I believe the answer is:
char
This clue is a double definition.
'make black' is the first definition.
(to char is to blacken by burning)
'tea' is the second definition.
(I've seen this before)
(Other definitions for char that I've seen before include "Daily cleaner; burn" , "Burn lightly" , "Overcook - fish - daily" , "Singe; a fish" , "Person who cleans" .)