Cockney wife's nationality … (5)

I believe the answer is:

dutch

I believe this clue is a double definition.

'cockney wife's' is the first definition.
(historic Cockney slang term for wife)

'nationality' is the second definition.

(Other definitions for dutch that I've seen before include "A European; pay-for-oneself (treat)" , "From Amsterdam, perhaps" , "partner" , "Netherlandish language" , "European - wife" .)

I've seen this clue in The Guardian.

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