Greet fantastic bird (5)
I believe the answer is:
egret
'bird' is the definition.
(I know that egret is a type of heron)
'greet fantastic' is the wordplay.
'fantastic' is an anagram indicator.
'greet' anagrammed gives 'EGRET'.
(Other definitions for egret that I've seen before include "Lesser white heron" , "White-feathered wading bird" , "One wading" , "Wading bird like a heron" , "White, plumed waterbird" .)