... cheater is beaten - ha! (7)
I believe the answer is:
hectare
'ha' is the definition.
('hectare' can be a synonym of 'ha')
'cheater is beaten' is the wordplay.
'is beaten' indicates an anagram.
'cheater' anagrammed gives 'HECTARE'.
(Other definitions for hectare that I've seen before include "Metric unit of area" , "Extent" , "10,000 squaer metres" , "The race (anag) - unit of area" , "Surface area equal to 10,000 square meters" .)