Remain to cover one's dissent (6)
I believe the answer is:
resist
'dissent' is the definition.
('resist' can be a synonym of 'dissent')
'remain to cover one's' is the wordplay.
'remain' becomes 'rest' ('rest' can be a synonym of 'remain').
'to cover' indicates putting letters inside.
'one's' becomes 'is' (roman numeral).
'rest' enclosing 'is' is 'RESIST'.
(Other definitions for resist that I've seen before include "Withstand, struggle against" , "Offer opposition to" , "Refuse to comply" , "Fight back" , "Hold out for sister" .)