Mark five notes (5)
I believe the answer is:
badge
'mark' is the definition.
(I know this)
'five notes' is the wordplay.
'five' becomes 'bad' (I am not sure about this - if you are sure you should give a lot more credence to this answer).
'notes' becomes 'ge'.
'bad'+'ge'='BADGE'
Can you help me to learn more?
(Other definitions for badge that I've seen before include "Insignia (of office?)" , "Form of identification" , "Thing worn to show, say, membership of organisation" , "Symbol worn for identification" , "Emblem of office" .)