Dame Edith, Sir Osbert or Sacheverell (7)
I believe the answer is:
sitwell
(Other definitions for sitwell that I've seen before include "Dame Edith --, English poet" , "English literary family" , "English poet, Edith, d. 1964" , "Writers Edith, Osbert" , "English poet (Edith, Osbert or Sacheverell)" .)