Staccato opposite (6)
I believe the answer is:
legato
'staccato opposite' is the definition.
(I've seen this in another clue)
This is all the clue.
(Other definitions for legato that I've seen before include "Musically smooth" , "Smoothly-flowing" , "In music, the opposite of staccato" , "Smoothly, musically speaking" , "running into each other" .)