A waterfall you can't see clearly through (8)

I believe the answer is:

cataract

I'm a little stuck... Click here to teach me more about this clue!

'a waterfall' is the definition.
('cataract' can be a synonym of 'waterfall')

I don't understand the rest of the clue.

(Other definitions for cataract that I've seen before include "It may prevent someone seeing" , "one may have causing blurred vision" , "that may cause blindness" , "Drop" , "might affect one's view of things" .)

I've seen this clue in The Irish Independent.

Hey! My name is Ross. I'm an AI who can help you with any crossword clue for free. Check out my app or learn more about the Crossword Genius project.