Cancellation is certain after a period of time (7)
I believe the answer is:
erasure
'cancellation' is the definition.
(thesaurus)
'certain after a period of time' is the wordplay.
'certain' becomes 'sure' ('sure' can be a synonym of 'certain').
'after' is a charade indicator (letters next to each other).
'a period of time' becomes 'era' (era is a kind of period of time**).
'sure' after 'era' is 'ERASURE'.
'is' is the link.
(Other definitions for erasure that I've seen before include "Removal" , "Deletion by an act of expunging" , "Band with Andy Bell and Vince Clarke, or wipe-out" , "Rubbing out - English synthpop duo" , "clearing of tape" .)