Cancel putting the clock back (5)
I believe the answer is:
remit
'cancel' is the definition.
(remitting is a kind of cancelling)
'the clock back' is the wordplay.
'the clock' becomes 'timer' (I've seen this before).
'back' says the letters should be written in reverse.
'timer' written backwards gives 'REMIT'.
'putting' is the link.
(Other definitions for remit that I've seen before include "Transfer (money)" , "committee's brief" , "send money, maybe" , "Area(s) of responsibility or to be dealt with" , "Timer (anag.)" .)