Send back right on time (5)
I believe the answer is:
remit
'send' is the definition.
(I've seen this in another clue)
'back right on time' is the wordplay.
'back' shows that the letters should be reversed in order.
'right' becomes 'r' (common abbreviation).
'on' means one lot of letters go next to another.
'r' after 'time' is 'timer'.
'timer' written backwards gives 'REMIT'.
(Other definitions for remit that I've seen before include "Area(s) of responsibility or to be dealt with" , "Abate; send (money)" , "Pardon (a sin)" , "Timer (anag.)" , "Defer" .)