Clock, perhaps, to send back (5)
I believe the answer is:
timer
'clock perhaps' is the definition.
(something which times)
'send back' is the wordplay.
'send' becomes 'remit' (I've seen this before).
'back' shows that the letters should be reversed in order.
'remit' backwards is 'TIMER'.
'to' acts as a link.
(Other definitions for timer that I've seen before include "One may have the minutes" , "Clock or watch" , "Trigger mechanism" , "Watch, for example" , "Eg, stopwatch" .)