Bushel part (4)
I believe the answer is:
peck
'bushel part' is the definition.
('peck' is part of 'bushel')
This is all the clue.
(Other definitions for peck that I've seen before include "Country; letter I (radio communications)" , "Bite lightly; a dry measure" , "Strike with beak" , "Kiss; old dry measure" , "Attack with beak" .)