Barley product (4)
I believe the answer is:
malt
'barley product' is the definition.
(I've seen this in another clue)
This is all the clue.
(Other definitions for malt that I've seen before include "Brewing ingredient derived from grain" , "Barley product used in brewing" , "Pre-soaked kiln-dried cereal grain" , "Cereal grain for distilling" , "Dried grain used for brewing and distilling" .)