Once seabird confronting Alan outside (8)
I believe the answer is:
external
'outside' is the definition.
(synonyms)
'once seabird confronting alan' is the wordplay.
'once' becomes 'ex' (prefix meaning former or onetime).
'seabird' becomes 'tern' (tern is a kind of seabird).
'confronting alan' becomes 'al' (I can't justify this - if you can you should believe this answer much more).
'ex'+'tern'+'al'='EXTERNAL'
Can you help me to learn more?
(Other definitions for external that I've seen before include "Lying outside" , "Coming from outside" , "abroad" , "Outward" , "Superficial" .)