The most common and most likely answer to this crossword clue is the 7 letter word SAMOYED
I've seen this crossword clue in The Daily Telegraph
S
A
M
O
Y
E
D
More clues leading to the result SAMOYED
- Appeal, instant, the solver once had, but not setter!
- Kind of dog, someday barking
- South American dictionary describing unknown dog
- Unhappy to involve doctor with the old dog
- Upsetting to involve doctor with the old dog
- Dose may upset Siberian dog
- Dog bones you found in grave
- Dog someday must be trained
- Supposing Miliband embraces twinkling 15 Down?
- Even this dog will have his day, some day perhaps!
Buddy explains!

The straight part
We know that "Dog" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case dog = samoyed.The cryptic/wordplay part
In cryptic crossword there's often an wordplay/cryptic part as well.This part involves a more complex hint, such as an anagram, homophone, hidden word, etc.
Sadly, We don't have an explanation for this specific crossword clue yet.
What does SAMOYED mean?
SAMOYED noun- A member of the Samoyedic peoples of the Siberian Urals, who speak Samoyedic languages
- A hardy breed of dog from Siberia