Even Madge agreed: just not a good — a fantastic superstar (4,4,7)

I haven't cracked this one yet — but the brilliant team at Times for the Times have:

Anagram [fantastic] of EVEN MADGE A{g}REED A [just not a G (good) – i.e. only one of the G’s]. I had fun finalising the anagrist here! For the surface reading, Madge Allsop was the long-suffering, silent “bridesmaid” of Dame Edna as played on stage and TV by the actress Emily Perry.