Yours truly for one dog! (6)
I believe the answer is:
setter
I believe this is a double definition.
'yours truly' is the first definition.
(the person that set this crossword)
'one dog' is the second definition.
(setter is a type of dog)
'for' is the link.
(Other definitions for setter that I've seen before include "One barking" , "Breed of dog - crossword compiler" , "pointer" , "Hunting dog" , "Puzzle creator" .)