Citizen, bound to be heard, large landowner (8,5)

I believe the answer is:
national trust
'be heard large landowner' is the definition.
The definition suggests a singular noun which matches the answer.
'citizen bound' is the wordplay.
'citizen' becomes 'national' (national can mean a citizen of a country).
'bound' becomes 'trust' (I am not sure about this - if you are sure you should believe this answer much more).
'national'+'trust'='NATIONAL TRUST'
'to' acts as a link.
Can you help me to learn more?
(Other definitions for national trust that I've seen before include "Society concerned with preservation" , "charitable organisation" , "Conservation organisation" , "Preserving organisation" , "Heritage conservation charity" .)
