A white cat in a street isn’t rare, ultimately (4,8)

'a white' is the definition.
Both the definition and answer are singular nouns.
Perhaps there's a link between them I don't understand?

'cat in a street isn't rare ultimately' is the wordplay.
I cannot really see how this works, but
'cat' could be 'puma' (puma is a kind of cat) and 'puma' is located in the answer.
'street' could be 'st' (abbreviation) and 'st' is found in the answer.
'isn't' could be 'isnt' and 'isnt' is present in the leftover letters.
The remaining letters 'ae' is a valid word which might be clued in a way I don't understand.
This may be the basis of the clue (or it may be nonsense).

Can you help me to learn more?