Like the wolf, superior in breeding (6)
I believe the answer is:
lupine
'breeding' is the definition.
Although both the answer and definition are singular nouns, I can't see how they can define each other.
'like the wolf superior in' is the wordplay.
I cannot really understand how this works, but
'superior' could be 'u' (I've seen this in other clues) and 'u' is found within the answer.
'in' is present in the answer.
This may be the basis of clue (or it may be nonsense).
Can you help me to learn more?
(Other definitions for lupine that I've seen before include "ike wolves" , "Like a wolf" , "Wolfish" , "Of or like wolves" , "like a wild animal" .)