A bushing is a cylindrical piece with a hole through the middle, like a short piece of pipe. Used basically for making a large hole smaller, sometimes for repair purposes and sometimes to line a soft material with a harder one for wear resistance. Et cetera. In this case the bronze bushing probably was to make a worn out hole a bit smaller and also to act as an anti-friction material. Should last longer than the original before wearing to an unreasonable amount of sloppiness.
Hope that helps.
-HM