Siberian drink (6)
I believe the answer is:
bitter
I believe this is a double definition.
'siberian' is the first definition.
(thesaurus)
'drink' is the second definition.
(bitter is a kind of drink)
(Other definitions for bitter that I've seen before include "Acerbic" , "Sharp-tasting or resentful" , "English beer, sounds sour" , "Resentful about English beer?" , "severe" .)