A drink for the head (6)
I believe the answer is:
noggin
I believe this clue is a double definition.
'a drink' is the first definition.
(drink measurement, typically a quarter of a pint)
'the head' is the second definition.
(noggin is a kind of head)
'for' is the link.
(Other definitions for noggin that I've seen before include "Small amount of alcohol" , "Gill usually" , "Drink, small quantity of it" , "Small measure of liquid" , "Measure of alcohol, about a quarter pint" .)