Perhaps people from Oslo are in gowns, partying (10)

I believe the answer is:

norwegians

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'perhaps people from oslo' is the definition.
I can't judge whether this defines the answer.

'are in gowns partying' is the wordplay.
'partying' is an anagram indicator (I've seen 'parties' mean this (the letters move or party around)).
'are'+'in'+'gowns'='areingowns'
'areingowns' anagrammed gives 'NORWEGIANS'.

Can you help me to learn more?

(Another definition for norwegians that I've seen is " Nationals".)

I've seen this clue in The Hindu.

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