Formerly fair, but not any more! (4,4)

'not any more' is the definition.
I know nothing about this answer so I can't tell whether it can be defined by this definition.

'formerly fair' is the wordplay.
I cannot quite understand how this works, but
'formerly' could be 'once' (synonyms) and 'once' is present in the answer.
'fair' could be 'just' (associated in meaning) and 'just' is found within the answer.
This accounts for all the letters.
This explanation may well be incorrect...

'but' is the link.

Can you help me to learn more?