Former bird taking almost everything outside (8)
I believe the answer is:
external
'outside' is the definition.
('external' is associated in meaning with 'outside')
'former bird taking almost everything' is the wordplay.
'former' becomes 'ex'.
'bird' becomes 'tern' (I've seen this before**).
'taking' is a charade indicator (letters next to each other).
'almost' means to remove the last letter (most of the word but not all of it).
'everything' becomes 'all' (I've seen this before).
'all' with its final letter taken off is 'al'.
'ex'+'tern'+'al'='EXTERNAL'
(Other definitions for external that I've seen before include "Belonging to the outside" , "abroad" , "Lying outside" , "Relating to the outside" , "Surface" .)