Bird demolished pretty morsel (6,6)
I believe the answer is:
stormy petrel
'bird' is the definition.
(stormy petrel is a kind of bird)
'demolished pretty morsel' is the wordplay.
'demolished' is an anagram indicator.
'pretty'+'morsel'='prettymorsel'
'prettymorsel' with letters rearranged gives 'STORMY-PETREL'.
(Other definitions for stormy petrel that I've seen before include "Mother Carey's chicken" , "Person who delights in controversy" , "portent of trouble" , "seabird" , "Popular name for sea bird believed to presage bad weather" .)