An animal and one flustered bird (6)
I believe the answer is:
pigeon
'bird' is the definition.
(pigeon is a kind of bird)
'an animal and one flustered' is the wordplay.
'an animal' becomes 'pig' (I've seen this in other clues).
'and' says to put letters next to each other.
'flustered' indicates an anagram.
'one' with letters rearranged gives 'eon'.
'pig'+'eon'='PIGEON'
(Other definitions for pigeon that I've seen before include "Bird of towns and woods" , "Dove-like bird" , "birdie" , "Bird with heavy body and short legs" , "Seed-eating bird" .)