Thin and weak-looking, unlike Rose (5)

I believe the answer is:

weedy

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'thin' is the definition.
(similar in meaning)

I cannot understand how the rest of the clue works.

(Other definitions for weedy that I've seen before include "scrawny" , "Underdeveloped" , "Thin, puny (colloq.)" , "like an untended flower bed?" , "Skinny" .)

I've seen this clue in the Evening Standard.

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