A sticky plant? (5)

I believe the answer is:

broom

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'plant?' is the definition.
(I know that Broom is Calcifuge)

I can't explain the remainder of the clue.

(Other definitions for broom that I've seen before include "Shrub and cleaning instrument" , "Yellow-flowering shrub" , "Plant - sweeper" , "cleaner" , "Flowering shrub" .)

I've seen this clue in the Evening Standard.

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