Stones gathered at bottom of cliff before new show (6)
I believe the answer is:
screen
'show' is the definition.
(screening is a kind of showing)
'stones gathered at bottom of cliff before new' is the wordplay.
'stones gathered at bottom of cliff' becomes 'scree'.
'before' says to put letters next to each other.
'new' becomes 'n'.
'scree'+'n'='SCREEN'
(Other definitions for screen that I've seen before include "Examine methodically" , "Flat surface onto which images are projected" , "Room partition; vet" , "put on show" , "Conceal; show (a film)" .)