Simple announcement of "A lemon tree, my dear Watson"? (8)

I believe the answer is:

homespun

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

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

(Other definitions for homespun that I've seen before include "Folksy - open mush (anag)" , "Simple, unsophisticated" , "Unsophisticated - not made in mill" , "Artless - posh menu (anag)" , "Artless and straightforward" .)

I've seen this clue in The Independent.

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