National Trust homes are investments, primarily (4)
I believe the answer is:
thai
'national' is the definition.
('Thai' is an example)
'trust homes are investments primarily' is the wordplay.
'primarily' suggests taking the first letters.
The initial letters of 'trust homes are investments' is 'THAI'.
(Other definitions for thai that I've seen before include "Easterner" , "One from Bangkok" , "nationality" , "Native of Southeast Asia" , "Morte d'16author" .)