Complete payment, perhaps, for stool? (8)

I believe the answer is:

footrest

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'for stool?' is the definition.
(footrest is a kind of stool)

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

(Other definitions for footrest that I've seen before include "Supporter" , "Sitter's leg support" , "Stool, perhaps" , "Support for sitter" , "Support for legs" .)

I've seen this clue in The Times.

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