Piece of Norman architecture (4)
I believe the answer is:
arch
'piece' is the definition.
(arch is a kind of piece)
I can't explain the remainder of the clue.
Can you help me to learn more?
(Other definitions for arch that I've seen before include "Marble, for example" , "Curved part of the foot" , "Consummate" , "Curved entrance" , "Coyly playful" .)