Old Empire lacking arms lacks backing (7)

I believe the answer is:

ottoman

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'old empire' is the definition.
(Ottoman Empire)

I can't explain the rest of the clue.

(Other definitions for ottoman that I've seen before include "Turk; low stuffed seat" , "Description of empire" , "Turkish empire or ling cushioned seat" , "cushion" , "Am not to (anag)" .)

I've seen this clue in The Globe and Mail.

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