My stars in firmament? (7)
I believe the answer is:
heavens
'firmament?' is the definition.
(synonyms)
I can't explain the remainder of the clue.
Can you help me to learn more?
(Other definitions for heavens that I've seen before include "Exclamation of surprise" , "Goodness" , "the blue" , "Sky - good grief!" , "Save hen (anag.)" .)