Tower guard's not a vegetarian, it seems (9)

I believe the answer is:

beefeater

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'tower guard's' is the definition.
(I've seen this before)

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

(Other definitions for beefeater that I've seen before include "Bodyguard of the British monarch" , "no vegetarian?" , "Yeoman of the Guard; carnivore" , "One might guard" , "Yeoman warder of the Tower of London" .)

I've seen this clue in The Daily Mail.

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