Measure of area (7)
I believe the answer is:
hectare
'measure of area' is the definition.
(I've seen this before)
This is the entire clue.
(Other definitions for hectare that I've seen before include "Surface area equal to 10,000 square meters" , "The race (anag) - unit of area" , "Ten thousand square metres" , "Metric land area" , "Some land in France" .)