Person who has issue receiving letters about diet (10)

I believe the answer is:

parliament

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'diet' is the definition.
(I've seen this before)

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

(Other definitions for parliament that I've seen before include "Legislative body" , "The law is laid down here" , "Diet" , "Legislative assembly" , "Houses" .)

I've seen this clue in The Guardian.

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