Like overfed cats? (3)

I believe the answer is:

fat

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'like' is the definition.
Both the answer and definition are adjectives. Perhaps you can see a link between them that I don't see?

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

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(Other definitions for fat that I've seen before include "Obese, overweight" , "Portly" , "Like 10 ac" , "Obese, having spare tyre etc" , "Naturally oily substance" .)

I've seen this clue in the Evening Standard.

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