Region in Far East (4)
I believe the answer is:
area
'region' is the definition.
(I know that area is a type of region)
'in far east' is the wordplay.
'in' indicates a hidden word.
'AREA' can be found hidden inside 'far east'.
(Other definitions for area that I've seen before include "Extent of a two-dimensional surface" , "Space for a specific purpose, say picnic" , "Expanse of a surface" , "Extent of a 2-dimensional surface" , "Part of a building, city etc" .)