Sorceress left out of magic group? (5)
I believe the answer is:
circe
'sorceress' is the definition.
(figure of Greek myth)
'left out of magic group?' is the wordplay.
'left' becomes 'l' (common abbreviation).
'out of' indicates named letters should be taken away.
'magic group?' becomes 'circle' (The Magic Circle, organisation of magicians).
'circle' with 'l' taken out is 'CIRCE'.
(Other definitions for circe that I've seen before include "Enchanting female" , "Siren" , "Greek sorceress who turned men into swine" , "Enchantress encountered by Odysseus" , "Greek sorceress who detained Odysseus on her island" .)