___ Hillary (with Sherpa Tenzing) first to climb Everest in 1953 (6)
I believe the answer is:
edmund
(Other definitions for edmund that I've seen before include "------ Ironside, Saxon King of England, 1016" , "- Blunden; - Burke" , "English king (939-946)" , "--- Spenser, Eng. poet" , "One of two kings of England, d. 946 and 1016, respectively" .)