Rafter; practise boxing (4)
I believe the answer is:
spar
I believe this clue is a double definition.
'rafter' is the first definition.
(I've seen this before)
'practise boxing' is the second definition.
(I've seen this before)
(Other definitions for spar that I've seen before include "Go a few rounds with the ship's pole" , "Scrap" , "Sticks" , "Box (gently) - fight (verbally)" , "Pole to support sails, rigging etc" .)