Time on hill in district (6)
I believe the answer is:
sector
'district' is the definition.
(thesaurus)
'time on hill' is the wordplay.
'time' becomes 'sec'.
'on' is a charade indicator (letters next to each other).
'hill' becomes 'tor' (tor is a kind of hill).
'sec'+'tor'='SECTOR'
'in' is the link.
(Other definitions for sector that I've seen before include "Specific group as part of the economy" , "District" , "Distinct part (of, eg, economy)" , "region" , "Area, division" .)