Birds providing old saint with wealth (9)
I believe the answer is:
ostriches
'birds' is the definition.
(ostrich is a kind of bird)
'old saint with wealth' is the wordplay.
'old' becomes 'o' (abbreviation as in OT - Old Testament).
'saint' becomes 'st' (abbreviation).
'with' says to put letters next to each other.
'wealth' becomes 'riches' (synonyms).
'o'+'st'+'riches'='OSTRICHES'
'providing' acts as a link.
(Other definitions for ostriches that I've seen before include "Largest living birds" , "People not facing the reality" , "Fast-running flightless birds" .)