Development of eastern nation (6)
I believe the answer is:
Here is my best explanation:
'development' is the definition.
'eastern nation' is the wordplay.
'eastern' becomes 'e'.
'nation' becomes 'state' ('state' can be a synonym of 'nation').
'of' acts as a link.
(Other definitions for estate that I've seen before include "Person's belongings after death", "All that one owns at death", "The whole of a deceased person's assets", "Nakedness", "Car with big luggage area", "Everything person possesses", "The whole of one's possessionsat death", "large car", "All money and property owned at time of death" and "Rank - housing development - car".)