Creed or opinion (6)
I believe the answer is:
belief
This clue is a double definition.
'creed' is the first definition.
(belief is a kind of creed)
'opinion' is the second definition.
(an opinion is a personal belief)
(Other definitions for belief that I've seen before include "Religious conviction" , "Trust, faith (6)" , "Persuasion" , "Creed or opinion" , "Tenet, creed" .)