Religiously, he's comparatively early (5)

I believe the answer is:
prior
'early' is the definition.
(thesaurus)
I don't understand how the remainder of the clue works.
Can you help me to learn more?
(Other definitions for prior that I've seen before include "Preceding" , "Clergyman - earlier" , "head of a house of friars" , "English keeper" , "More pressing" .)
