In the Kent area it’s where builders may be working (4)
I believe the answer is:
site
'where builders may be working' is the definition.
(as in a building site)
'in the kent area it's' is the wordplay.
'in' is an insertion indicator.
'the kent area' becomes 'se' (Kent is in the South East of England).
'it's' becomes 'it' (I've seen this in other clues).
'se' enclosing 'it' is 'SITE'.
(Other definitions for site that I've seen before include "Locale" , "Area set aside for building" , "Spot, location" , "Somewhere to build, perhaps" , "Location (of building, dig etc)" .)