Smallholders, historically old, residing in the country (6)
I believe the answer is:
yeomen
'smallholders historically' is the definition.
'old residing in the country' is the wordplay.
'old' becomes 'o' (common abbreviation eg in OE for Old English).
'residing in' is an insertion indicator.
'the country' becomes 'yemen' (Yemen is an example).
'o' put inside 'yemen' is 'YEOMEN'.
(Other definitions for yeomen that I've seen before include "Freeholders (historical)" , "naval signallers" , "Small farmers (historical)" , "Freeholders (hist.)" , "farmers of old" .)