Use some of the notes to play an organ piece (4)
I believe the answer is:
stop
'an organ piece' is the definition.
(I've seen this in another clue)
'use some of the notes to play' is the wordplay.
'use some of' indicates the answer is hidden within the clue (I've seen 'using some' mean this).
'STOP' is hidden in the letters of 'the notes to play'.
(Other definitions for stop that I've seen before include "Withhold payment" , "Intercept" , "Cease, halt" , "Knock out" , "break" .)