Can scoff but it saves time in the kitchen (11,4)

I believe the answer is:

convenience food

'it saves time in the kitchen' is the definition.
(food requiring little or no preparation)

'can scoff' is the wordplay.
'can' becomes 'convenience' (both can mean toilet).
'scoff' becomes 'food' (scoff can informally mean food).
'convenience'+'food'='CONVENIENCE FOOD'

'but' acts as a link.

I've seen this clue in The Guardian.

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