Heartlessly allow bird to suffer — animal! (4,4)
I believe the answer is:
wild boar
'animal' is the definition.
(thesaurus)
'heartlessly allow bird to suffer' is the wordplay.
'heartlessly' suggests removing the centre.
'to suffer' indicates an anagram (I've seen 'suffers' mean this).
'allow' with its middle removed is 'alow'.
'alow'+'bird'='alowbird'
'alowbird' with letters rearranged gives 'WILD BOAR'.
(Other definitions for wild boar that I've seen before include "strong meat" , "Untamed pig" , "Feral pig" , "Non-domesticated pig" , "Game" .)