Recognise a catholic commendation (8)
I believe the answer is:
accredit
'recognise' is the definition.
(synonyms)
'a catholic commendation' is the wordplay.
'catholic' becomes 'C' (abbreviation as in RC for Roman Catholic).
'commendation' becomes 'credit' (credit is a kind of commendation).
'a'+'c'+'credit'='ACCREDIT'
(Other definitions for accredit that I've seen before include "Certify, ascribe" , "Give official recognition to" , "Give official sanction to (a diplomat)" , "Show to be correct" , "Attribute (something to)" .)