Dry hill area (6)
I believe the answer is:
'area' is the definition.
(I know that area can be written as sector)
'dry hill' is the wordplay.
'dry' becomes 'sec' (similar in meaning).
'hill' becomes 'tor' (tor is a kind of hill).
(Other definitions for sector that I've seen before include "Escort in zone" , "Corset (anag) - part of a circle" , "Part of circle between radii" , "Area, division" , "Division or part" .)