Dog eats a large dead bird (4,5)
I believe the answer is:
bald eagle
'bird' is the definition.
(bald eagle is a kind of bird)
'dog eats a large dead' is the wordplay.
'dog' becomes 'beagle' (beagle is a kind of dog).
'eats' is an insertion indicator.
'large' becomes 'L' (eg in clothes sizes).
'dead' becomes 'd' (abbreviation in government records).
'a'+'l'+'d'='ald'
'beagle' enclosing 'ald' is 'BALD EAGLE'.
(Other definitions for bald eagle that I've seen before include "National emblem of the USA" , "US national bird" , "National bird of the USA" , "Flier" , "N. American bird" .)