Some solve the riddle in the heavens (5)
I believe the answer is:
ether
'heavens' is the definition.
(I've seen this in another clue)
'some solve the riddle in' is the wordplay.
'some' indicates the answer is hidden within the clue (some of the parts of the word are used).
'ETHER' is hidden in the letters of 'solve the riddle in'.
'the' acts as a link.
(Other definitions for ether that I've seen before include "Volatile organic liquid once used as a general anaesthetic" , "Chemical solvent" , "Formerly an anaesthetic" , "It could knock you out" , "Some were put out by this" .)