Left unploughed and unseeded (6)
I believe the answer is:
fallow
'left unploughed and unseeded' is the definition.
(I've seen this before)
This is all the clue.
(Other definitions for fallow that I've seen before include "Undeveloped but potentially useful" , "idle" , "Left unploughed and unseeded" , "(Of land) left unsown" , "Uncultivated" .)