Oscar Wilde's glassy, angular 'Miss' (5)
I believe the answer is:
prism
'miss' is the definition.
Although both the answer and definition are singular nouns, I cannot see how one could define the other.
I don't understand the rest of the clue.
Can you help me to learn more?
(Other definitions for prism that I've seen before include "Glass triangle that separates white light into the colour spectrum" , "Three-sided object that separates light into colours" , "White light splitter" , "Prims (anag)" , "Light beam splitter" .)