Fight to get beam (4)
I believe the answer is:
spar
I believe this clue is a double definition.
'fight' is the first definition.
(sparring is a kind of fighting)
'beam' is the second definition.
(I've seen this before)
'to get' acts as a link.
(Other definitions for spar that I've seen before include "Stout pole to support rigging" , "Raps with large timber" , "Raps with large beam" , "microcrystalline mineral?" , "possibly rigged" .)