A driven sort of occupier (7)
I believe the answer is:
invader
'occupier' is the definition.
The definition and answer can be both people as well as being singular nouns.
Maybe you can see an association between them that I can't see?
'a driven sort' is the wordplay.
'sort' indicates anagramming the letters.
'a'+'driven'='adriven'
'adriven' anagrammed gives 'INVADER'.
'of' is the link.
Can you help me to learn more?
(Other definitions for invader that I've seen before include "Attacker from outside" , "Military intruder" , "Trespasser" , "One attacks" , "One illegally entering" .)