Landholder of the old sultanate (6)
I believe the answer is:
yeoman
'landholder' is the definition.
(yeoman is a kind of landholder)
'the old sultanate' is the wordplay.
'the old' becomes 'ye'.
'sultanate' becomes 'oman' (I've seen this in other clues).
'ye'+'oman'='YEOMAN'
'of' is the link.
(Other definitions for yeoman that I've seen before include "16th-century freeholder of a small farm" , "Historically, English freeholders and footsoldiers" , "Royal attendant" , "farmer with his own land" , "One may (anag.)" .)