He fetches a dog (9)
I believe the answer is:
retriever
'a dog' is the definition.
(retriever is a kind of dog)
I don't understand how the remainder of the clue works.
Can you help me to learn more?
(Other definitions for retriever that I've seen before include "Dog bred to fetch game" , "Breed of dog" , "making a complete recovery?" , "Hound" , "someone to set the situation right?" .)