Box with headgear (4)
I believe the answer is:
spar
'box with headgear' is the definition.
(I've seen this in another clue)
This is the entire clue.
(Other definitions for spar that I've seen before include "Pole used to support sails or rigging" , "dispute" , "What boxers do" , "Mineral; box; wing beam" , "Close friend" .)