Singer shows there's nothing in taking the corner correctly (7)

I believe the answer is:

crooner

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'singer' is the definition.
(I know that crooner is a type of singer)

I cannot understand how the rest of the clue works.

Can you help me to learn more?

(Other definitions for crooner that I've seen before include "Singer like Bing and Frank" , "Bing Crosby, for example" , "Singer of quiet songs" , "Crosby-type singer" , "One who sings like Bing?" .)

I've seen this clue in The Irish Independent.

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