Crossword Genius

On which to have a potato in comfort? (5)

Ross

I believe the answer is:

couch

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'comfort?' is the definition.
Although both the answer and definition are singular nouns, I can't see how they can define each other.

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

Can you help me to learn more?

(Other definitions for couch that I've seen before include "Long seat; grass" , "Grass; reclining seat" , "Upholstered seat for more than one" , "something comfortable to sit on" , "express" .)

I've seen this clue in the Evening Standard.
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