Pastime for first-class passengers on a night flight, or curious gang in Ritz in South Africa, perhaps? (10)

I believe the answer is:

stargazing

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'pastime' is the definition.
The answer and definition can be both acts as well as being singular nouns.
Perhaps there's an association between them I don't understand?

I cannot understand how the rest of the clue works.

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I've seen this clue in The Irish Times.

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