Heartless Harry removed bird of mixed ancestry (6)
I believe the answer is:
hybrid
'of mixed ancestry' is the definition.
(I've seen this before)
'heartless harry removed bird' is the wordplay.
'heartless' says to hollow out the word (remove centre letters).
'removed' indicates an anagram (moved again).
'harry' with its centre removed is 'hy'.
'bird' anagrammed gives 'brid'.
'hy'+'brid'='HYBRID'
(Other definitions for hybrid that I've seen before include "Plant grown from two different species" , "Offspring of mixed parents" , "Plant bred from two varieties" , "Crossed offspring" , "Crossbred" .)