Super prince made king more positive (5)
I believe the answer is:
surer
'more positive' is the definition.
('sure' can be similar in meaning to 'positive')
'super prince made king' is the wordplay.
I cannot really understand how this works, but
'king' could be 'er' (abbreviation for Edward Rex, various English kings) and 'er' is present in the answer.
The remaining letters 'sur' is a valid word which might be clued in a way I don't understand.
This explanation may well be incorrect...
Can you help me to learn more?
(Other definitions for surer that I've seen before include "faster" , "More certain and positive" , "more right?" .)