Needing to play, sad losing slide (9)
I believe the answer is:
glissando
'slide' is the definition.
(sliding musical effect)
'needing to play sad losing' is the wordplay.
'needing to play' indicates an anagram (letters play around).
'sad'+'losing'='sadlosing'
'sadlosing' is an anagram of 'GLISSANDO'.
(Other definitions for glissando that I've seen before include "Sliding series of notes (mus.)" , "Slide between two notes" , "Re-interpreting this musical direction" , "Effect produced by playing a series of notes very rapidly" , "Sliding effect in moving from one musical note to another" .)