Working group of small proportions fencing area in province (7)
I believe the answer is:
ontario
'province' is the definition.
(province of Canada)
'working group of small proportions fencing area' is the wordplay.
'working' becomes 'on' (on can mean working or activated).
'group of small proportions' becomes 'trio' (group of three).
'fencing' means one lot of letters goes inside another (to fence can mean to contain or put a limit round).
'area' becomes 'a' (maths abbreviation).
'trio' enclosing 'a' is 'tario'.
'on'+'tario'='ONTARIO'
'in' is the link.
(Other definitions for ontario that I've seen before include "Most easterly Great Lake" , "A North American lake" , "provincial area" , "Canadian Great lakes province" , "Canadian province and Great Lake" .)