Bitter plant? How singular! (4)

I believe the answer is:

aloe

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'bitter plant?' is the definition.
(I've seen this in another clue)

I cannot understand how the rest of the clue works.

Can you help me to learn more?

(Other definitions for aloe that I've seen before include "shrub" , "has a bitter taste" , "Bitter fruit" , "Succulent plant (4) 5532" , "Flower, maybe vera" .)

I've seen this clue in the Evening Standard.

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