Religion is a virtue (5)
I believe the answer is:
faith
I believe this is a double definition.
'religion' is the first definition.
(synonyms)
'virtue' is the second definition.
'is a' acts as a link.
(Other definitions for faith that I've seen before include "Unshakeable belief" , "Confidence" , "religion" , "Strong belief in a supernatural power" , "Total trust" .)