Barley bristle (3)
I believe the answer is:
awn
'barley bristle' is the definition.
(I've seen this in another clue)
This is the entire clue.
(Other definitions for awn that I've seen before include "Grass "beard"" , "Bristle on grass spikelet" , "Bristly head of barley sheath, quite wan" , "Beard growing from an ear of barley or rye" , "Bristly growth" .)