Bird of prey following black dog (6)
I believe the answer is:
beagle
'dog' is the definition.
(beagle is a kind of dog)
'bird of prey following black' is the wordplay.
'bird of prey' becomes 'eagle' (eagle is a kind of bird of prey).
'following' says to put letters next to each other.
'black' becomes 'b' (as in pencil classifications).
'eagle' put after 'b' is 'BEAGLE'.
(Other definitions for beagle that I've seen before include "Small hunting dog" , "Darwin voyaged in this ship" , "Small, sturdy breed of hound" , "HMS - was Darwin's ship; hunting dog" , "Short-haired dog" .)