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 before)
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" .)