Excessively chubby marsupial almost eats bagel in Garden City (9)

'garden city' is the definition.
Both the answer and definition are singular nouns.
Perhaps there's an association between them I don't understand?

'excessively chubby marsupial almost eats bagel' is the wordplay.
I cannot quite understand how this works, but
'excessively' could be 'too' (to too great a degree) and 'too' is found within the answer.
'bagel' could be 'o' (bagel can mean a score of zero in tennis) and 'o' is located in the answer.
This may be the basis of the clue (or it may be nonsense).

'in' acts as a link.

Can you help me to learn more?