Citizen with confidence in charitable organisation (8,5)
I believe the answer is:
national trust
'charitable organisation' is the definition.
(UK conservation society)
'citizen with confidence' is the wordplay.
'citizen' becomes 'national' (national can mean a citizen of a country).
'with' says to put letters next to each other.
'confidence' becomes 'trust' (synonyms).
'national'+'trust'='NATIONAL TRUST'
'in' acts as a link.
(Other definitions for national trust that I've seen before include "Heritage organisation" , "Preservationists" , "Heritage conservation charity" , "charitable organisation" , "Preservation body" .)