One to welcome dawn crossing bridge with one's dog (6,7)
I believe the answer is:
cocker spaniel
'one to welcome dawn crossing bridge' is the definition.
I can't judge whether this defines the answer.
'one's dog' is the wordplay.
'one's' becomes 'cocker' (I am not sure about this - if you are sure you should believe this answer much more).
'dog' becomes 'spaniel' (spaniel is a kind of dog).
'cocker'+'spaniel'='COCKER SPANIEL'
'with' acts as a link.
Can you help me to learn more?
(Other definitions for cocker spaniel that I've seen before include "Small dog used in game shooting" , "Breed of gun dog" , "Ponies crackle (anag) - dog" , "Mutt" , "Breed of small dog" .)