Drink of fire (4)
I believe the answer is:
sack
This clue is a double definition.
'drink' is the first definition.
(sack is a kind of drink)
'fire' is the second definition.
(dismiss someone from their job)
'of' acts as a link.
(Other definitions for sack that I've seen before include "Wine; fire; bag" , "Dismiss; plunder; wine" , "present holder" , "Dismiss; an old wine" , "Flour or grain bag" .)