That great explorer (5)
I believe the answer is:
scott
I believe this is a double definition.
'that great' is the first definition.
(I've seen this before)
'explorer' is the second definition.
(Robert Falcon Scott, Scott of the Antarctic)
(Other definitions for scott that I've seen before include "Ivanhoe author" , "old novelist" , "British Antarctic explorer, died 1912" , "He died leading Antarctic expedition" , "Sir Walter --, writer" .)