Heavens, poetically (5)
I believe the answer is:
ether
'heavens poetically' is the definition.
(I've seen this in another clue)
This is all the clue.
(Other definitions for ether that I've seen before include "It could knock you out" , "Formerly an anaesthetic" , "Solvent; clear sky (poet.)" , "Chemical solvent" , "Volatile solvent" .)