Eradication is certain after a long time (7)
I believe the answer is:
erasure
'eradication' is the definition.
Although both the answer and definition are singular nouns, I can't see how they can define each other.
'certain after a long time' is the wordplay.
'certain' becomes 'sure' (similar in meaning).
'after' is a charade indicator (letters next to each other).
'a long time' becomes 'era' (a long period of time).
'sure' after 'era' is 'ERASURE'.
'is' acts as a link.
Can you help me to learn more?
(Other definitions for erasure that I've seen before include "Removal" , "group from the 80s" , "Band with Andy Bell and Vince Clarke, or wipe-out" , "clearing of tape" , "Obliteration - rare use (anag)" .)