Fruit with the top off is still fruit (6)

I believe the answer is:

ananas

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'fruit' is the definition.
(ananas is a kind of fruit)

I cannot understand how the remainder of the clue works.

(Other definitions for ananas that I've seen before include "F" , "Black top on this fruit" , "piece of fruit" , "Sort of fruit" , "Pineapple" .)

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

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