Assistant in a Herculean labor (5)
I believe the answer is:
atlas
'assistant in a herculean labor' 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 "God" , "A geog. book; N. African range" , "Chart book" , "Book of maps or charts" , "Titan with a fearsome burden" .)