Eye problem (8)
(Other definitions for cataract that I've seen before include "Cascade; eye defect" , "Waterfall which might be seen in the eye" , "what may have a bad effect on the viewer" , "Force" , "can obstruct your view" .)
'eye problem' is the definition.
(I've seen this in another clue)
This is the entire clue.
(Other definitions for stye that I've seen before include "Observer's problem" , "Infected swelling of the eye" , "nasty spot" , "Eyelid problem" , "Climb" .)