Pursuer (6)
I believe the answer is:
chaser
'pursuer' is the definition.
(I know that pursuer can be written as chaser)
This is the entire clue.
(Other definitions for chaser that I've seen before include "Hunter; drink" , "one in the national hunt" , "Racing horse" , "A drink like beer after whisky" , "Drink that follows immediately after another one" .)