The Penguin Concerto? (7)

I believe the answer is:

emperor

I'm a little stuck... Click here to teach me more about this clue!

This clue could be a double definition.

'the penguin' is the first definition.
(emperor penguin is a kind of penguin)

'concerto?' is the second definition.
Although both the answer and definition are singular nouns, I cannot see how they can define each other.

Can you help me to learn more?

(Other definitions for emperor that I've seen before include "Large richly-coloured butterfly" , "Eg, Caesar" , "Absolute ruler" , "Nero or penguin" , "Supreme ruler" .)

I've seen this clue in The Sun.

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