Setter say, initially waffling, remains nonsense (7)
I believe the answer is:
'nonsense' is the definition.
'setter say initially waffling remains' is the wordplay.
'setter' becomes 'i' (the person that set the crossword).
'say' indicates a 'sounds like' (homophone) clue.
'initially' says to take the initial letters.
'remains' becomes 'ash' (I've seen this before).
The first letter of 'waffling' is 'w'.
'i' is a homophone of 'eye'.
(Other definitions for eyewash that I've seen before include "Optic solution to relieve irritation - rubbish!" , "Visual cleansing agent - nonsense" , "Fiddlesticks" , "Insincere talk or optical lotion" , "Nonsense; cleansing lotion" .)