Backing strikes you fight (4)
I believe the answer is:
spar
'fight' is the definition.
(I know that spar is a more specific form of fight)
'backing strikes' is the wordplay.
'backing' shows that the letters should be reversed in order.
'strikes' becomes 'raps' (rapping is a kind of striking).
'raps' reversed gives 'SPAR'.
'you' is the link.
(Other definitions for spar that I've seen before include "Pole to support sails, rigging etc" , "Translucent mineral" , "Raps with large timber" , "A mineral; nautical pole" , "Stout pole, nautically" .)