Stop for a whisky (6)
I believe the answer is:
scotch
I believe this clue is a double definition.
'stop' is the first definition.
(I've seen this before)
'whisky' is the second definition.
(I know that Scotch is a type of whisky)
'for a' is the link.
(Other definitions for scotch that I've seen before include "Whisky from Scotland" , "Type of egg" , "hard drink" , "Prevent -- frustrate" , "Kind of whisky spelt thus" .)