A new adjacent short entrance leading to wing (6)
I believe the answer is:
annexe
'to wing' is the definition.
(synonyms)
'a new adjacent short entrance leading' is the wordplay.
'a' becomes 'an'.
'new' becomes 'n' (common abbreviation eg NT for New Testament).
'adjacent short entrance leading' becomes 'exe' (I can't explain this - if you can you should give a lot more credence to this answer).
'an'+'n'+'exe'='ANNEXE'
Can you help me to learn more?
(Other definitions for annexe that I've seen before include "Additional building" , "Conservatory, e.g." , "Addition that extends a main building" , "Extra accommodation block" , "Joined-on building" .)