Exit to open air (7)
I believe the answer is:
outdoor
'air' is the definition.
(I have seen 'open air' mean 'outdoor' so perhaps 'air' could also mean 'outdoor')
'exit to open' is the wordplay.
'exit' becomes 'door' (I've seen this in another clue).
'to' is a charade indicator (letters next to each other) (I've seen this in other clues).
'open' becomes 'out' (I've seen this in other clues).
'door' put after 'out' is 'OUTDOOR'.
(Other definitions for outdoor that I've seen before include "Alfresco - sort of pursuits" , "Not done in the house" , "Open-air" , "Located in the open air" , "in the garden, say" .)