Shows rock debris navvies cleared out (7)
I believe the answer is:
screens
'shows' is the definition.
(screening is a kind of showing)
'rock debris navvies cleared out' is the wordplay.
'rock debris' becomes 'scree' (I've seen this before).
'cleared out' means to remove the middle letters.
'navvies' with its centre removed is 'ns'.
'scree'+'ns'='SCREENS'
(Other definitions for screens that I've seen before include "vets" , "Checks" , "for security guards" , "Shows on the telly" , "Covers to conceal" .)