Guardian for one needing to rely on charity (8,5)
I believe the answer is:
national trust
'charity' is the definition.
(preservation charity)
'guardian for one needing to rely on' is the wordplay.
'guardian for one' becomes 'national' (the Guardian is a national newspaper).
'needing' is a charade indicator (letters next to each other).
'to rely on' becomes 'trust' (synonyms).
'national'+'trust'='NATIONAL TRUST'
(Other definitions for national trust that I've seen before include "Preserving organisation" , "charitable organisation" , "Preservationists" , "Conservation organisation" , "Conservationist organisation" .)