Zone of Far East (4)
I believe the answer is:
area
'zone' is the definition.
(thesaurus)
'of far east' is the wordplay.
'of' indicates a hidden word.
'AREA' can be found hidden inside 'far east'.
(Other definitions for area that I've seen before include "Field of activity or surface" , "Patch" , "'Tract, region (4)'" , "Extent of a 2-dimensional surface" , "Locality" .)