Strongman of myth (5)
'strongman of myth' is the definition.
(I've seen this in another clue)
This is the entire clue.
(Other definitions for atlas that I've seen before include "Album of maps" , "Legendary weightlifter" , "Sort of book" , "It appears at the top of the spine" , "I carry a huge weight" .)
(Other definitions for hercules that I've seen before include "In Greek myth, a hero noted for great strength and 12 labours" , "Strong hero" , "Twelve-labours myth. hero" , "Greek hero who carried out 12 labours" , "Fabled performer of labours" .)