Send the metronome back? (5)
I believe the answer is:
remit
'send the metronome back?' is the definition.
'remit' can be an answer for 'send' (I've seen this before). I'm not sure about the 'the metronome back?' bit.
'send the' is the wordplay.
'send' becomes 'remi' (I can't explain this - if you can you should give a lot more credence to this answer).
'the' becomes 't' (the is pronounced as a 't' sound in some dialects).
'remi'+'t'='REMIT'
Can you help me to learn more?
(Other definitions for remit that I've seen before include "Pardon (a sin)" , "Orders" , "Pay for timer" , "Desist from" , "Send - scope of one's duties" .)