Some climbing on Everest vanished (4)
I believe the answer is:
gone
'vanished' is the definition.
(gone can mean vanished or disappeared)
'some climbing on everest' is the wordplay.
'some' indicates a hidden word (some of the parts of the word are used).
'GONE' can be found hidden inside 'climbing on everest'.
(Other definitions for gone that I've seen before include "Departed or dead" , "... saga of 2's civil war" , "Departed or no longer available" , "Moved - died" , "No longer present" .)