Add extra material to half of Wagner's Ring, perhaps (7)

I believe the answer is:

lardner

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'ring perhaps' is the definition.
'lardner' can be an answer for 'ring' (I've seen this in another clue). I am not certain of the 'perhaps' bit.

I don't understand the remainder of the clue.

Can you help me to learn more?

I've seen this clue in The Times.

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