Heading north, look angry with a fog? (7)
I believe the answer is:
'fog?' is the definition.
(fog is a kind of aerosol)
'heading north look angry with a' is the wordplay.
'heading north' says the letters should be written backwards.
'look' becomes 'lo'.
'angry' becomes 'sore' ('sore' can be similar in meaning to 'angry'**).
'with' is a charade indicator (letters next to each other).
'losore' reversed gives 'erosol'.
'erosol' after 'a' is 'AEROSOL'.
(Other definitions for aerosol that I've seen before include "It dispenses liquid in a fine spray", "Liquid in a container under pressure", "See 17 down [CONTAINER]: under pressure", "Container with device for releasing contents as fine spray", "Spray producer".)