The most common and most likely answer to this crossword clue is the 7 letter word BOW-WOW
I've seen this crossword clue in Financial Times
B
O
W
-
W
O
W
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 = bow-wow.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 BOW-WOW mean?
BOW-WOW noun- The sound of a dog barking.
- A dog.
- (of language) Grandiose.
- Representing the sound of a dog barking.