Mrs Fawlty (5)
I believe the answer is:
sybil
'mrs fawlty' is the definition.
(Sybil Fawlty from the sitcom Fawlty Towers)
This is all the clue.
(Other definitions for sybil that I've seen before include "Basil Fawlty's wife" , "Female oracle; Mrs Fawlty" , "--- Thorndike, Fawlty" , "Dame - Thorndike, English actress" .)