Sky supporter of myth (5)
I believe the answer is:
atlas
'sky supporter 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 "One greatly burdened" , "book of world records?" , "Asian satin" , "In Greek myth, a Titan made to support the heavens" , "Holder of world" .)