They play at Olympics, then in almost an extra final battle (8,7)

I believe the answer is:

national anthems

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'they play at olympics' is the definition.
The definition suggests an adverb but the answer is not.

'then in almost an extra final battle' is the wordplay.
'final' indicates one should take the final letters.
'battle' indicates anagramming the letters (the letters disrupted as if in battle).
The final letter of 'extra' is 'a'.
'then'+'in'+'almost'+'an'+'a'='theninalmostana'
'theninalmostana' is an anagram of 'NATIONAL ANTHEMS'.

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I've seen this clue in the Sydney Morning Herald.

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