Region of Far East (4)
I believe the answer is:
area
'region' is the definition.
(I know that area is a type of region)
'of far east' is the wordplay.
'of' indicates a hidden word.
'AREA' is hidden in the letters of 'far east'.
(Other definitions for area that I've seen before include "Extent of a 2-dimensional surface" , "Region, zone" , "Surface measurement" , "Expanse of a surface" , "Geographical region" .)