Cereal husks (4)
I believe the answer is:
bran
'cereal husks' is the definition.
(I've seen this before)
This is all the clue.
(Other definitions for bran that I've seen before include "Food for horses in barn" , "Healthy breakfast" , "Husks of cereal seeds sifted from flour" , "Element in high fibre diet" , "Refuse from grain" .)