He had the weight of the world on his shoulders (5)
I believe the answer is:
atlas
'he had the weight of the world on his shoulders' is the definition.
(I've seen this in another clue)
This is all the clue.
(Other definitions for atlas that I've seen before include "Reference work" , "Plans" , "collection of charts" , "Segment of spine" , "Titan who bore the sky on his shoulders" .)