Writer’s retainer, heading off, enthralled by these in Calais (9)

I believe the answer is:

cervantes

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'writer's' is the definition.
(Miguel de Cervantes)

I don't understand how the rest of the clue works.

(Other definitions for cervantes that I've seen before include "Bookmaker" , "Spanish writer" , "Author of the novel 'Don Quixote'" .)

I've seen this clue in The Times.

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