More certain or more confident (5)
I believe the answer is:
surer
I believe this clue is a double definition.
'more certain' is the first definition.
('sure' can be a synonym of 'certain')
'more confident' is the second definition.
('sure' can be similar in meaning to 'confident')
'or' acts as a link.
(Other definitions for surer that I've seen before include "more right?" , "faster" , "More certain and positive" .)