It's just a formality for Luke (5)

I believe the answer is:

lucas

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'luke' is the definition.
Both the answer and definition are singular nouns.
Perhaps there's an association between them I don't understand?

I can't explain the rest of the clue.

Can you help me to learn more?

(Other definitions for lucas that I've seen before include "George --, creator of Star Wars" , "George -, US film director (Star Wars)" .)

I've seen this clue in the Evening Standard.

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