Air a number of points (4)
I believe the answer is:
mien
'air' is the definition.
(I've seen this in another clue)
'a number of points' is the wordplay.
'a number of' becomes 'mi' (I can't justify this - if you can you should give a lot more credence to this answer).
'points' becomes 'en' (two compass points).
'mi'+'en'='MIEN'
Can you help me to learn more?
(Other definitions for mien that I've seen before include "A face - maybe mine" , "Person's bearing" , "Dignified manner" , "A face like mine" , "A person's demeanour" .)