Dog, barking terrier, biting vet endlessly (9)
I believe the answer is:
retriever
'dog' is the definition.
(eg a Golden Retriever)
'barking terrier biting vet endlessly' is the wordplay.
'barking' is an anagram indicator (I've seen this in other clues).
'biting' is an insertion indicator (I've seen this in other clues).
'endlessly' means to remove the last letter.
'terrier' anagrammed gives 'retrier'.
'vet' with its final letter removed is 've'.
'retrier' placed around 've' is 'RETRIEVER'.
(Other definitions for retriever that I've seen before include "Working dog" , "someone to set the situation right?" , "He brings back" , "Gun-dog, may be golden" , "making a complete recovery?" .)