Green grass (3)
I believe the answer is:
rye
'green grass' is the definition.
(I've seen this in another clue)
This is all the clue.
(Other definitions for rye that I've seen before include "Cereal grass - Sussex Cinque Port" , "East Sussex resort" , "A Cinque Port; a grain" , "Bitterly regret" , "Grain used in flour and whiskey" .)