The most common and most likely answer to this crossword clue is the 8 letter word CERBERUS
C
E
R
B
E
R
U
S
More clues leading to the result CERBERUS
- Dog running around in certain British sports field
- In retrospect, playground superb, having banished quiet crazy demonic dog
- Given beers, cur turns to Hound of Hades
- Vicious gatekeeper who found employment in Barking?
- Mythical 19’s remarkably secure about British retreat
- Bar, secure, managed without a fearsome guard dog
- Heads off to deal with this gatekeeper?
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 = cerberus.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.