Ring fits EP RN. Clearly is means of identification (12)

I believe the answer is:

fingerprints

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'means of identification' is the definition.
(someone might be identified by their fingerprints)

'ring fits ep rn clearly' is the wordplay.
'ring fits ep rn' anagrams to 'FINGERPRINTS'.
But, I am unsure how the anagram is indicated.

'is' is the link.

Can you help me to learn more?

(Another definition for fingerprints that I've seen is " Marks of individuality".)

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

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