___ Gwyn, actress and Charles II's mistress, d. 1687 (4)
I believe the answer is:
nell
(Other definitions for nell that I've seen before include "- - Gwynne" , "-- Gwyn, 17th-century actress" , "Orphan girl" , "-- Gwyn, mistress of Charles II" , "Little -, (Dickens char.)" .)