Vet duo ridiculously pious (6)
I believe the answer is:
devout
'pious' is the definition.
(synonyms)
'vet duo ridiculously' is the wordplay.
'ridiculously' is an anagram indicator.
'vet'+'duo'='vetduo'
'vetduo' is an anagram of 'DEVOUT'.
(Other definitions for devout that I've seen before include "Pious, given to prayer" , "Pious and worshipful" , "Reverent" , "Pious, prayerful" , "Earnestly religious, prayerful" .)