1979 film drama starring Dustin Hoffman and Vanessa Redgrave (6)
I believe the answer is:
agatha
(Other definitions for agatha that I've seen before include "Aunt of Wooster" , "Bertie Wooster's aunt" , "Girl" , "Writer who created Hercule Poirot, . . . . . . Christie" , "- Christie, twentieth century crime novelist" .)