Tense, but happy to get drunk (7)
I believe the answer is:
uptight
'tense' is the definition.
('uptight' can be similar in meaning to 'tense')
'happy to get drunk' is the wordplay.
'happy' becomes 'up' (I've seen this in other clues).
'to get' means one lot of letters go next to another.
'drunk' becomes 'tight' (I've seen this in other clues**).
'up'+'tight'='UPTIGHT'
'but' is the link.
(Other definitions for uptight that I've seen before include "Tensely repressed" , "On edge" , "Informally nervous and tense" , "Informal word for nervously tense" , "Showing repressed anxiety or anger" .)