Person worthy of credibility (8)
I believe the answer is:
official
I believe this is a double definition.
'person' is the first definition.
(official is a kind of person)
'worthy of credibility' is the second definition.
(I've seen this before)
(Other definitions for official that I've seen before include "Authorative" , "One is in a position of authority" , "Bureaucrat" , "executive" , "Having authority to administer rules" .)