Two-dimensional measurement (4)
I believe the answer is:
area
'two-dimensional measurement' is the definition.
(I've seen this in another clue)
This is all the clue.
(Other definitions for area that I've seen before include "Expanse or neighbourhood" , "Region, space" , "'Tract, region (4)'" , "Succession, order" , "Extent of a 2-dimensional surface" .)