Horse feed (4)
I believe the answer is:
oats
'horse feed' is the definition.
(I've seen this in another clue)
This is the entire clue.
(Other definitions for oats that I've seen before include "Cereal for porridge" , "Wild ones are sown in youthful excess" , "Cereal food for horses" , "Cereal grass and seeds" , "Edible grass seeds" .)