Subject of a will (6)
I believe the answer is:
'subject of a will' is the definition.
(I've seen this in another clue)
This is the entire clue.
(Other definitions for estate that I've seen before include "Demesne" , "Extent of one's property" , "Total possessions" , "Housing area" , "Piece of land with a large house or many small ones" .)