Floor couple used in back office, reportedly (4)

I believe the answer is:

kayo

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

I cannot understand how the remainder of the clue works.

(Other definitions for kayo that I've seen before include "floor" , "Knockout" , "Conclusive end of a boxing match" , "Conclusion of a bout" , "Fight's ending" .)

I've seen this clue in the Independent.

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