Comfortable seat one’s lost in capital (4)

I believe the answer is:

sofa

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'comfortable seat' is the definition.
'sofa' can be an answer for 'seat' (sofa is a kind of seat). I am not certain of the 'comfortable' bit.

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

Can you help me to learn more?

(Other definitions for sofa that I've seen before include "Living room seat" , "Oafs (anag.)" , "Long upholstered seat with back and arms" , "Wide padded seat" , "Area for sitting" .)

I've seen this clue in The Times.

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