After restraint certain to get cover again (8)
I believe the answer is:
reinsure
'cover again' is the definition.
('insure' can be a synonym for 'cover' so perhaps 'reinsure' is OK for 'cover again')
'after restraint certain' is the wordplay.
'after' is a charade indicator (letters next to each other).
'restraint' becomes 'rein' (I've seen this before).
'certain' becomes 'sure' (synonyms).
'rein'+'sure' is 'REINSURE'.
'to get' is the link.
(Other definitions for reinsure that I've seen before include "Take out another policy" , "recover?" , "Cover again" , "Pass on a risk of having to pay compensation" .)