The most common and most likely answer to this crossword clue is the 10 letter word SALMONELLA
I've seen this crossword clue in Financial Times
S
A
L
M
O
N
E
L
L
A
More clues leading to the result SALMONELLA
- Diner's complaint, given pink articles used in bodega?
- Poisonous bacteria girl found on fish
- Nasty bug one got in small busy US city
- Girl is after fish causing disease
- Distinguished gathering admitting married woman with bug
- Bacterium may be found on all meals badly cooked
- Fish carried by girl reveals bacteria
- Bacteria developed on all meals
- Angrily slam a large city’s complaint
Buddy explains!

The straight part
We know that "Nasty bug" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case nasty bug = salmonella.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 SALMONELLA mean?
SALMONELLA noun- Any of several rod-shaped bacteria, of the genus Salmonella, that cause food poisoning and other diseases