Grass in Sussex location (3)
I believe the answer is:
rye
'grass' is the definition.
(I know that rye is a type of cereal)
I can't explain the remainder of the clue.
Can you help me to learn more?
(Other definitions for rye that I've seen before include "One of Cinque Ports" , "Hardy cereal crop" , "Hard liquor" , "Hardy annual cereal grass" , "East Sussex resort" .)