William Walton's Façade is based on poems by Edith ____ (7)
I believe the answer is:
sitwell
(Other definitions for sitwell that I've seen before include "English poet and critic, d. 1964" , "Dame Edith --, English poet" , "Writers Edith, Osbert" , "English poet (Edith, Osbert or Sacheverell)" , "Literary Dame" .)