Spray (8)
(Other definitions for nasal that I've seen before include "Pertaining to the nose" , "Like some spray" , "of a prominent feature" , "Of noses" , "Nosey" .)
'spray' is the definition.
(as in an aerosol spray)
This is the entire clue.
(Other definitions for aerosol that I've seen before include "air-freshener possibly required" , "source of graffiti?" , "Container with device for releasing contents as fine spray" , "See 17 down [CONTAINER]: under pressure" , "Pressurized container" .)
'spray' is the definition.
(I know that spray can be written as atomiser)
This is all the clue.
(Other definitions for atomiser that I've seen before include "Mister" , "Perfume spray" , "Device for making liquid into a fine spray" , "Device for reducing liquid to a fine spray" , "Spraying device - same riot (anag)" .)