Titularly, John Wayne (4)

I believe the answer is:

duke

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'john wayne' is the definition.
(I know that john wayne can be written as Duke)

I can't explain the rest of the clue.

(Other definitions for duke that I've seen before include "Highest ranked British peer" , "Lord" , "Member of the nobility" , "Nobleman of the highest rank" , "Highest ranking British peer" .)

I've seen this clue in the Evening Standard.

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