That part of a cereal plant containing the seeds (3)
I believe the answer is:
ear
'that part of a cereal plant containing the seeds' is the definition.
(I've seen this before)
This is all the clue.
(Other definitions for ear that I've seen before include "good sense of music" , "Spike (wheat)" , "Hearing aid?" , "Lug (colloq.)" , "Organ inside heart" .)