Pay the bill at the chiropodist's? (4)

I believe the answer is:

foot

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'pay' is the definition.
(as in footing the bill)

I cannot understand how the rest of the clue works.

(Other definitions for foot that I've seen before include "Measure - part of body" , "Infantry - unit of linear measure" , "Distance to the end of a limb?" , "Imperial distance" , "See 24" .)

I've seen this clue in the Evening Standard.

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