Some land bill: concerning! (4)
I believe the answer is:
acre
'some land' is the definition.
(unit of land)
'bill concerning' is the wordplay.
'bill' becomes 'ac' (abbreviation for account).
'concerning' becomes 're' (both can mean on a particular topic).
'ac'+'re'='ACRE'
(Other definitions for acre that I've seen before include "Old unit of area - old port" , "Persistent tendency" , "Unit of area of 4,840 square yards" , "Area measure - Israeli port - Brazilian state" , "Imperial land measure" .)