Forms part of this puzzle's theme? (6)
I believe the answer is:
shapes
'forms' is the definition.
(I know this)
I don't understand the rest of the clue.
Can you help me to learn more?
(Other definitions for shapes that I've seen before include "Forms, outlines" , "Casts or moulds" , "10, 17 and 22, for example" , "models" , "Oblong and square, say" .)