The most common and most likely answer to this crossword clue is the 5 letter word ANNOY
I've seen this crossword clue in The Guardian
A
N
N
O
Y
More clues leading to the result ANNOY
- Mayonnaise sent back contains this bug
- Trouble repulsed in Lyon, naturally
- Bother man, non-Tory, on regular basis
- Simple refusal stops a bit of bother
- Anger some when accepting refusal
- Bug? There’s a small number in a place over the pond
- No time for speaker to get angry
- Speaker doesn’t begin to try
- Some mayonnaise poured back to drive you crazy
- Bug in PA system? Time’s lost
Buddy explains!

The straight part
We know that "Bug" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case bug = annoy.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 ANNOY mean?
ANNOY noun- A feeling of discomfort or vexation caused by what one dislikes.
- That which causes such a feeling.
- To disturb or irritate, especially by continued or repeated acts; to bother with unpleasant deeds.
- To do something to upset or anger someone; to be troublesome.
- To molest; to harm; to injure.