The most common and most likely answer to this crossword clue is the 6 letter word PLAGUE
I've seen this crossword clue in Financial Times
P
L
A
G
U
E
More clues leading to the result PLAGUE
- Curse city for changing sides
- Harry‘s little medal good for Queen
- Capital changes hands for dog
- Epidemic in the city before 9
- Soaring mountain road missing from visitant’s haunt
- 8 down said to be about this in London, where capital is changing hands
- Pester power contrary local girl used regularly
- Losing a friend with fever and disease
- Mountain’s gone over by half of visitors, causing bother
- Trial prompted by political volte-face in capital
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 = plague.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 PLAGUE mean?
PLAGUE noun- (often used with the, sometimes capitalized: the Plague) The bubonic plague, the pestilent disease caused by the virulent bacterium Yersinia pestis.
- An epidemic or pandemic caused by any pestilence, but specifically by the above disease.
- A widespread affliction, calamity or destructive influx, especially when seen as divine retribution.
- A grave nuisance, whatever greatly irritates.
- Collective noun for common grackles
- To harass, pester or annoy someone persistently or incessantly.
- To afflict with a disease or other calamity.