Makes certain (7)
'makes certain' is the definition.
('ensure' can be a synonym of 'make certain')
This is the entire clue.
(Other definitions for ensures that I've seen before include "Makes safe or certain" , "Warrant" , "guarantees" .)
'makes certain' is the definition.
('assure' can be a synonym of 'make certain')
This is all the clue.
(Other definitions for assures that I've seen before include "Gives confidence or covers with a policy" , "Informs with certainty and confidence" , "guarantees" , "Tells to dispel any doubts" , "States positively and confidently" .)