Piece of art (4)

I believe the answer is:
opus
(Other definitions for opus that I've seen before include "Soup (anag.)" , "Musical composition in the soup" , "Piece of music (with number)" , "Major work" , "Composition - magnum __" .)
I believe the answer is:
opus
(Other definitions for opus that I've seen before include "Soup (anag.)" , "Musical composition in the soup" , "Piece of music (with number)" , "Major work" , "Composition - magnum __" .)