Region is part of Far East (4)
I believe the answer is:
area
'region' is the definition.
(area is a kind of region)
'part of far east' is the wordplay.
'part of' indicates a hidden word.
'AREA' is hidden in the letters of 'far east'.
'is' is the link.
(Other definitions for area that I've seen before include "District; locale" , "The measure of a surface" , "Region; extent of a surface" , "'Tract, region (4)'" , "Extent of a two-dimensional surface" .)