Check stony slope before noon (6)
I believe the answer is:
screen
'check' is the definition.
(synonyms)
I don't understand the rest of the clue.
Can you help me to learn more?
(Other definitions for screen that I've seen before include "Films are projected onto it" , "Veil; vet" , "Movable partition - cinema" , "put on show" , "Flat surface onto which images are projected" .)