Large waterfalls and eye defects (9)
I believe the answer is:
cataracts
'large waterfalls and eye defects' is the definition.
(I've seen this before)
This is the entire clue.
(Other definitions for cataracts that I've seen before include "Large waterfalls and eye defects" , "Waterfalls in the eyes?" , "Waterfalls and eye diseases" , "Eye problems causing blurred vision" , "Eye afflictions produce waterfalls" .)