Where those in service eat dog's dinner (4)

I believe the answer is:

mess

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'dog's dinner' is the definition.
(I've seen this before)

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

(Other definitions for mess that I've seen before include "Untidy muddle" , "Meal" , "dish" , "Confused situation" , "Where sailors eat" .)

I've seen this clue in The Sun, The Telegraph and The Times.

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