At heart envisions playful, amazing style - prefiguring, maybe, a linear arrangement (6)
I believe the answer is:
syzygy
'at' is the definition.
Although both the answer and definition are singular nouns, I cannot understand how they can define each other.
I don't understand how the remainder of the clue works.
Can you help me to learn more?
(Other definitions for syzygy that I've seen before include "couple" , "Eclipse condition" , "Conjunction or opposition" , "appearance of new moon" , "line-up of stars, perhaps" .)