Oriental trees? Nonsense! (7)

I believe the answer is:

eyewash

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'nonsense' is the definition.
(I've seen this before)

I don't understand how the rest of the clue works.

(Other definitions for eyewash that I've seen before include "Nonsense (informal)" , "Nonsense; cleansing lotion" , "Nonsense (colloq.)" , "Bunk" , "Optic lotion - nonsense!" .)

I've seen this clue in The Globe and Mail.

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