Husks of cereal grain (4)
I believe the answer is:
bran
'husks of cereal grain' is the definition.
(I've seen this before)
This is all the clue.
(Other definitions for bran that I've seen before include "Coarse meal for horses" , "Husks of corn" , "Husks after milling" , "Milled grain husk" , "Horse-food in barn" .)