Word before "plane" or "projection" (6)
I believe the answer is:
astral
'word before plane or projection' is the definition.
(I've seen this in another clue)
This is all the clue.
(Other definitions for astral that I've seen before include "Pertaining to the stars" , "Starry sort of altars." , "Related to the stars" , "Like the stars" , "To do with stars on altars" .)