Quarter; subdivision (6)
I believe the answer is:
sector
I believe this is a double definition.
'quarter' is the first definition.
(I've seen this before)
'subdivision' is the second definition.
(I have seen 'Subdivision of area ' mean 'sector' so perhaps 'subdivision' could also mean 'sector')
(Other definitions for sector that I've seen before include "Corset for part of battle area" , "Social group that forms part of a society or economy" , "Area of circle between two radii" , "Area covered by corset" , "District" .)