As Sybil said, she's a sorceress (5)
I believe the answer is:
sibyl
'a sorceress' is the definition.
The answer and definition can be both people as well as being singular nouns.
Maybe there's a link between them I don't understand?
'as sybil said she's' is the wordplay.
'sybil' can be anagrammed to 'SIBYL'.
Though, I am unsure how the anagram is indicated.
Can you help me to learn more?
(Other definitions for sibyl that I've seen before include "Woman mouthpiece of a god, uttering prophecies" , "Charmer" , "Greek prophetess" , "Seer in classical times" , "Greek oracle" .)