Yard part (4)
I believe the answer is:
foot
'yard part' is the definition.
('foot' is part of 'yard')
This is the entire clue.
(Other definitions for foot that I've seen before include "Imperial distance" , "Infantry - unit of linear measure" , "Twelve inches" , "Labour Party leader, 1980-83" , "Distance to the end of a limb?" .)