Reportedly assume lupine identity in ancient English poem (7)

I believe the answer is:

beowulf

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'poem' is the definition.
Both the definition and answer are singular nouns.
Perhaps there's a link between them I don't understand?

I don't understand the remainder of the clue.

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(Other definitions for beowulf that I've seen before include "[SCAN-DIN-AVIAN] poem" , "Germanic hero" , "An old tale" , "Anglo-Saxon epic poem" , "Old English saga" .)

I've seen this clue in The Times.

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