Figures in old place of worship briefly lowering top of altar (9)
I believe the answer is:
octahedra
'figures' is the definition.
(I've seen this before)
I cannot understand how the remainder of the clue works.
Can you help me to learn more?
(Other definitions for octahedra that I've seen before include "things with many faces" , "Solid artefacts" , "solid objects" , "Solid figures with eight plane faces" , "shapes" .)