The most common and most likely answer to this crossword clue is the 5 letter word SPITZ
I've seen this crossword clue in The Guardian
S
P
I
T
Z
More clues leading to the result SPITZ
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 = spitz.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 SPITZ mean?
SPITZ noun- Any of several Nordic breeds of dog such as the Pomeranian or Samoyed