Feel sorry for headless bird (5)
I believe the answer is:
egret
'bird' is the definition.
(egret is a kind of bird)
'feel sorry for headless' is the wordplay.
'feel sorry for' becomes 'regret' (I've seen this before).
'headless' means to remove the first letter.
'regret' with its initial letter removed is 'EGRET'.
(Other definitions for egret that I've seen before include "white fish eater" , "(Usually) white heron" , "White-plumed wader" , "Wading bird like a heron" , "Wader with white plumage" .)