Sliding note (9)
I believe the answer is:
glissando
'sliding note' is the definition.
(I've seen this before)
This is the entire clue.
(Other definitions for glissando that I've seen before include "Re-interpreting this musical direction" , "(Musically) a rapid series of ascending or descending notes" , "Sliding effect in moving from one musical note to another" , "Musical flourish" , "Note with sliding pitch" .)