A sieve (6)
I believe the answer is:
screen
'a sieve' is the definition.
(I know that screen is a more specific form of sieve)
This is all the clue.
(Other definitions for screen that I've seen before include "Conceal; show (a film)" , "Movable partitions" , "Cover - cinema" , "Test or examine for the presence of disease or infection" , "Examine methodically" .)