Fancy drink with attitude (7)
I believe the answer is:
suppose
'fancy' is the definition.
(both can mean to guess or suspect)
'drink with attitude' is the wordplay.
'drink' becomes 'sup' (to sup is to drink).
'with' is a charade indicator (letters next to each other).
'attitude' becomes 'pose' (attitude can mean a pose or stance).
'sup'+'pose'='SUPPOSE'
(Other definitions for suppose that I've seen before include "'Believe, perhaps on uncertain grounds (7)'" , "Expect" , "Assume without proof" , "Hypothesize" , "Reckon, think" .)