Send money or return the watch (5)
I believe the answer is:
'send money' is the definition.
(I've seen this in another clue)
'return the watch' is the wordplay.
'return' is a reversal indicator.
'the watch' becomes 'timer' (I've seen this before).
'timer' backwards is 'REMIT'.
'or' acts as a link.
(Other definitions for remit that I've seen before include "Send; abate; cancel" , "Send back; scope of authority" , "Orders" , "Send (money) in payment; pardon" , "Dispatch" .)