Thirsty, swallow single drink (3,7)
I believe the answer is:
dry martini
'drink' is the definition.
(I've seen this before)
'thirsty swallow single' is the wordplay.
'thirsty' becomes 'dry' (similar in meaning).
'swallow' becomes 'martin' (martin is a kind of swallow).
'single' becomes 'I' (one).
'dry'+'martin'+'i'='DRY MARTINI'
(Other definitions for dry martini that I've seen before include "drink" , "Gin-based cocktail" .)