Far Eastern diet (4)
I believe the answer is:
fare
'diet' is the definition.
(I've seen this before)
'far eastern' is the wordplay.
'eastern' becomes 'e'.
'far'+'e'='FARE'
(Other definitions for fare that I've seen before include "Cost of travel" , "Paying passenger" , "Taxi passenger; food" , "Food, or price of bus ticket" , "diet" .)