Race round area (4)
I believe the answer is:
acre
'area' is the definition.
(I've seen this before)
'race round' is the wordplay.
'round' is an anagram indicator.
'race' with letters rearranged gives 'ACRE'.
(Other definitions for acre that I've seen before include "Unit of area of 4,840 square yards" , "Care about this bit of land" , "Mediterranean port" , "4840 sq yds" , "holy city" .)