Some arable agricultural land (3)
I believe the answer is:
lea
'land' is the definition.
(I've seen this before)
'some arable agricultural' is the wordplay.
'some' says the answer is hidden in the clue (some of the parts of the word are used).
'LEA' is hidden within 'arable agricultural'.
(Other definitions for lea that I've seen before include "Open pasture" , "Grazing land" , "Land growing grass" , "River of east London" , "''The lowing herd winds slowly o'er the ... '' (Gray)" .)