Goalpost part (8)
I believe the answer is:
crossbar
'goalpost part' is the definition.
('crossbar' is part of 'goalpost')
This is the entire clue.
(Other definitions for crossbar that I've seen before include "Part of bicycle or goal" , "Bit of sports equipment" , "Goal's top member" , "Horizontal beam over goal posts" , "Helps to define the goal" .)