Waterfall perhaps needs operation? (8)
I believe the answer is:
cataract
'waterfall' is the definition.
(synonyms)
'needs operation?' is the wordplay.
I cannot quite see how this works, but
'operation?' could be 'act' (operation is a kind of act) and 'act' is found within the answer.
This may be the basis of the clue (or it may be nonsense).
'perhaps' acts as a link.
Can you help me to learn more?
(Other definitions for cataract that I've seen before include "It may prevent someone seeing" , "Waterfall and eye disease" , "Large waterfall" , "makes it hard to see" , "Waterfall - eye complaint" .)