Two cats on drums (7)
I believe the answer is:
tomtoms
'drums' is the definition.
(tomtom is a kind of drum)
'two cats on' is the wordplay.
'two' becomes 'tom' (I am not sure about this - if you are sure you should give a lot more credence to this answer).
'cats' becomes 'toms' (tom is a kind of cat).
'on' says to put letters next to each other.
'tom'+'toms'='TOMTOMS'
Can you help me to learn more?
(Other definitions for tomtoms that I've seen before include "Navigational aids" , "seen in part of the kitchen" .)