Old place name red-top rag reprinted (9)

I believe the answer is:

petrograd

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'old place name' is the definition.
Although both the answer and definition are singular nouns, I cannot see how one could define the other.

'red-top rag reprinted' is the wordplay.
'reprinted' indicates an anagram.
'red'+'top'+'rag'='redtoprag'
'redtoprag' anagrammed gives 'PETROGRAD'.

Can you help me to learn more?

I've seen this clue in The Independent.

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