Wallet for holding pound notes (6)
I believe the answer is:
folder
'wallet' is the definition.
(a wallet for documents)
'for holding pound notes' is the wordplay.
'holding' indicates putting letters inside.
'pound' becomes 'l'.
'notes' becomes 'de' (two musical notes).
'l'+'de'='lde'
'for' going around 'lde' is 'FOLDER'.
(Other definitions for folder that I've seen before include "Thin file for papers" , "Wallet (for papers)" , "Cover for loose papers" , "Binder" , "Document cover" .)