Argentinian perhaps showing her composure? Quite the opposite! (8)

I believe the answer is:

hispanic

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'opposite' is the definition.
The definition and answer can be both people as well as being singular nouns.
Maybe you can see an association between them that I don't see?

I don't understand how the rest of the clue works.

Can you help me to learn more?

(Other definitions for hispanic that I've seen before include "Spanish-speaking American" , "like Don Quixote" , "Relating to Spain/Spanish" , "Latin" , "Relating to Spanish-speaking countries" .)

I've seen this clue in The Guardian.

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