Proprietors (6)
I believe the answer is:
owners
'proprietors' is the definition.
('owner' can be a synonym of 'proprietor')
This is the entire clue.
(Other definitions for owners that I've seen before include "Legal possessors" , "Worsen for possessors" , "Proprietors" , "Holders, possessors" , "Those in lawful possession, as of house" .)