Ageless English bird almost everybody goes after (7)
I believe the answer is:
eternal
'ageless' is the definition.
('eternal' can be a synonym of 'ageless')
'english bird almost everybody goes after' is the wordplay.
'english' becomes 'e' (abbreviation).
'bird' becomes 'tern' (tern is a kind of bird**).
'almost' means to remove the last letter (most of the word but not all of it).
'everybody' becomes 'all' (I've seen this before).
'goes after' says to put letters next to each other.
'all' with its last letter taken off is 'al'.
'e'+'tern'+'al'='ETERNAL'
(Other definitions for eternal that I've seen before include "Timeless" , "with lasting benefit" , "Existing forever" , "going on for ever" , "Forever and always" .)