Note on instrument one's played (5)
I believe the answer is:
viola
'one's played' is the definition.
(viola is a musical instrument)
'note on instrument' is the wordplay.
'note' becomes 'a' (musical note).
'on' means one lot of letters go next to another.
'instrument' becomes 'viol' (viol is a kind of instrument).
'a' put after 'viol' is 'VIOLA'.
(Other definitions for viola that I've seen before include "part of Shakespeare" , "Bloomer" , "Pansy-like plant" , "Pansy-like flower" , "Shakespeare heroine; instrument" .)