Cockney idiolect (7,5)

I believe the answer is:

rhyming slang

(Other definitions for rhyming slang that I've seen before include "Titfer, butcher's and porky, for example" , "Cockney idiom" , ""Apples and pears" for stairs, for example" , "Eg "apples" for "stairs"" , "Cockney poetical chatter" .)

I've seen this clue in The Guardian.

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