Black bird sees dog (6)
I believe the answer is:
beagle
'dog' is the definition.
(beagle is a kind of dog)
'black bird' is the wordplay.
'black' becomes 'b' (as in pencil classifications).
'bird' becomes 'eagle' (eagle is a type of bird).
'b'+'eagle'='BEAGLE'
'sees' is the link.
(Other definitions for beagle that I've seen before include "Hunting hound" , "Hunting dog followed on foot" , "hunting animal with smooth coat" , "Breed of dog in a glebe" , "HMS - was Darwin's ship; hunting dog" .)