Something popular with children, or the direct opposite (10)

I believe the answer is:

roundabout

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'opposite' is the definition.
Both the definition and answer are adjectives. Perhaps you can see an association between them that I can't see?

I cannot understand how the remainder of the clue works.

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(Other definitions for roundabout that I've seen before include "Circuitous" , "Ride" , "Traffic controller" , "Indirect" , "usually circulatory" .)

I've seen this clue in the Evening Standard.

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