Second drink (6)
I believe the answer is:
chaser
'second drink' is the definition.
(I've seen this in another clue)
This is all the clue.
(Other definitions for chaser that I've seen before include "Drink following one of another sort" , "Different kind of drink - horse" , "A drink like beer after whisky" , "Pursuer - of beer after whiskey?" , "Horse; drink following another" .)