A shade unsuitable for wet weather (7)

I believe the answer is:

parasol

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'a shade' is the definition.
(parasol is a kind of shade)

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

(Other definitions for parasol that I've seen before include "mushroom" , "aeroplane" , "It's put up to provide shade" , "Sunshade" , "Protection from sun" .)

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

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