FA rubbish about Chelsea's first mogul (3,3)

I believe the answer is:

fat cat

I'm a little stuck... Click here to teach me more about this clue!

'mogul' is the definition.
Both the definition and answer are singular nouns.
Perhaps they are linked in a way I don't understand?

'fa rubbish about chelsea's first' is the wordplay.
'rubbish' becomes 'tat' (low-quality items or material).
'about' indicates putting letters inside.
'chelsea's first' becomes 'c' (1st letter of 'chelsea').
'tat' enclosing 'c' is 'tcat'.
'fa'+'tcat'='FAT CAT'

Can you help me to learn more?

(Other definitions for fat cat that I've seen before include "Wealthy person like obese feline" , "Rich person or obese feline" , "Banking executive maybe" , "Big cheese" , "pampered pet" .)

I've seen this clue in The Sun.

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