Meant to wander under steadfast sky (9)
I believe the answer is:
firmament
'sky' is the definition.
(I've seen this before)
'meant to wander under steadfast' is the wordplay.
'to wander' is an anagram indicator.
'under' says to put letters next to each other.
'steadfast' becomes 'firm' (synonyms).
'meant' with letters rearranged gives 'ament'.
'ament' put after 'firm' is 'FIRMAMENT'.
(Other definitions for firmament that I've seen before include "Heavens, sky" , "Sky (literary)" , "The starry heaven" , "outer space, encapsulated" , "The celestial sphere" .)