Expel entry in the open air (7)
I believe the answer is:
outdoor
'in the open air' is the definition.
(I've seen this before)
'expel entry' is the wordplay.
'expel' becomes 'out' (I can't explain this - if you can you should believe this answer much more).
'entry' becomes 'door' (synonyms).
'out'+'door'='OUTDOOR'
Can you help me to learn more?
(Other definitions for outdoor that I've seen before include "Alfresco - sort of pursuits" , "Done in the open" , "exposed to the elements" , "External" , "Al fresco" .)