Crossword Genius

Not one of those minibars! (4,4)

Ross

I believe the answer is:

bath soap

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'not one' is the definition.
Although both the answer and definition are singular nouns, I don't see how one could define the other.

I cannot understand how the rest of the clue works.

Can you help me to learn more?

I've seen this clue in the Evening Standard.
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