Expert accepts right to some land (4)
I believe the answer is:
acre
'land' is the definition.
(I've seen this before)
'expert accepts right to some' is the wordplay.
'expert' becomes 'ace' (ace is a kind of expert**).
'accepts' is an insertion indicator.
'to some' indicates taking the first letters.
The first letter of 'right' is 'r'.
'ace' placed around 'r' is 'ACRE'.
(Other definitions for acre that I've seen before include "Square measure of land" , "Care about this bit of land" , "marine location in Israel" , "region of ground" , "once occupied by Crusaders" .)