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 wordplay.
'drunk' indicates anagramming the letters.
'alegot' with letters rearranged gives 'LEGATO'.
(Other definitions for legato that I've seen before include "Smooth, flowing (music)", "scored smoothly", "In music, in a smooth even manner", "play on without pause", "running into each other", "Smooth, flowing (mus.)", "Played smoothly", "to be played smoothly", "Smoothly flowing in style" and "with smooth execution".)