Smooth ale got drunk (6)
I believe the answer is:
legato
'smooth' is the definition.
('legato' can be similar in meaning to 'smooth')
'ale got drunk' is the wordplay.
'drunk' indicates anagramming the letters.
'ale'+'got'='alegot'
'alegot' with letters rearranged gives 'LEGATO'.
(Other definitions for legato that I've seen before include "Smoothly (musical)" , "Smoothly flowing (music)" , "(Music) without breaks between notes" , "with smooth execution" , "Musically smooth" .)