Tubby Tom, a rich guy! (3,3)

I believe the answer is:

fat cat

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'a rich guy' is the definition.
The definition suggests a singular noun which matches the answer.

'tubby tom' is the wordplay.
'tubby' becomes 'fat' (both can mean plump).
'tom' becomes 'cat' (a tom is a male cat).
'fat'+'cat'='FAT-CAT'

Can you help me to learn more?

(Other definitions for fat cat that I've seen before include "Overpaid industrialist" , "Very wealthy person, especially an industrialist" , "One wealthy, overpaid" , "Magnate" , "Wealthy and privileged person" .)

I've seen this clue in the Sydney Morning Herald.

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