The sister of Goneril and Cordelia? (5)
I believe the answer is:
regan
'the sister of goneril and cordelia?' is the definition.
(I've seen this in another clue)
This is all the clue.
(Other definitions for regan that I've seen before include "Daughter of King Lear" , "better half of Cornwall" , "Work team" , "Possessed gir" , "part of 1 25 [KING LEAR]" .)