He’s fixed up with a modest country dwelling (9)
I believe the answer is:
homestead
'country dwelling' is the definition.
(homestead can mean a farm house)
'he's fixed up with a modest' is the wordplay.
'fixed up with' is an anagram indicator (the order of letters must be fixed).
'a'+'modest'='amodest'
'he' with its letters anagrammed with 'amodest' makes 'HOMESTEAD'.
(Other definitions for homestead that I've seen before include "House with adjoining farm" , "Dwelling" , "US ranch house" , "House of station" .)