Try this cocktail if in need of a drink (7)
I believe the answer is:
thirsty
'in need of a drink' is the definition.
(I've seen this in another clue)
'try this cocktail' is the wordplay.
'cocktail' is an anagram indicator.
'try'+'this'='trythis'
'trythis' anagrammed gives 'THIRSTY'.
'if' is the link.
(Other definitions for thirsty that I've seen before include "Needing moisture" , "Try this if you need drink" , "Needing a tipple" , "Wanting a drink" , "Hungry" .)