Smooth ale got drunk (6)
I believe the answer is:
Here is my best explanation:
'smooth' is the definition.
('legato' can be similar in meaning to 'smooth')
'ale got drunk' is the subsidiary indication.
'drunk' is an anagram indicator.
'alegot' anagrammed gives 'legato'.
(Other definitions for legato that I've seen before include "Smooth, flowing (mus.)", "(Of music) smoothly", "Smooth, flowing (music)", "Smoothly, musically speaking", "In music, the opposite of staccato", "Musically smooth", "Smoothly (mus.)", "In a smooth and flowing manner (music)", "Got ale (anag.)" and "Smoothly flowing in style".)