I would first accurately investigate the location of the fungus - by looking at small light source reflections from coating surface (like LED flashlight) you can count and tell which surface has fungus.

If fungus is under 1st or 2nd element, then you can try to make a special spanning wrench to unscrew the front securing ring located around front lens element, then accurately extract 1st and 2nd elements for cleaning. Make sure you mark their radial orientaiton to put exactly at same angle during assembly. I never did it with XF 56mm, but removed front fastening ring on XF 100-400mm lens, and perhaps there is a securing glue in XF 56mm.

However if fungus is under 3rd element or further - then it is only possible to access by complete disassembly of rear area.

Also, if fungus is between 4th and 5th elements - then it is a very difficult problem, because that elements are glued together, and that type of cleaning requires extremely complex process of separating glass, cleaning and optically cementing them back.

The ball goes into the spring loaded socket of aperture ring.