Spotted best friend bearing down on goal — just tops! (8,3)
I believe the answer is:
carriage dog
'spotted best friend' is the definition.
Although both the answer and definition are singular nouns, I cannot see how one could define the other.
'bearing down on goal just tops' is the wordplay.
I cannot quite understand how this works, but
'bearing' could be 'carriage' (someone's stance or posture) and 'carriage' is found within the answer.
'down' could be 'd' and 'd' is located in the answer.
This may be the basis of the clue (or it may be nonsense).
Can you help me to learn more?
(Another definition for carriage dog that I've seen is " Dalmatian (archaic)".)