Eastern trees? Nonsense! (7)
I believe the answer is:
eyewash
'nonsense' is the definition.
(I've seen this before)
I can't explain the rest of the clue.
Can you help me to learn more?
(Other definitions for eyewash that I've seen before include "Nonsense (informal)" , "Visual cleansing agent - nonsense" , "Bunk" , "rot?" , "Nonsense; cleansing lotion" .)