Explorer Heyerdahl (4)
I believe the answer is:
thor
'explorer heyerdahl' is the definition.
(I've seen this in another clue)
This is all the clue.
(Other definitions for thor that I've seen before include "Norse hammer-wielding god" , "Mythical figure" , "Norse god of war" , "Norse god for whom Thursday is named" , "Comic superhero" .)