The most common and most likely answer to this crossword clue is the 7 letter word WHISKER
I've seen this crossword clue in The Times
W
H
I
S
K
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More clues leading to the result WHISKER
Buddy explains!

The straight part
We know that "Bristle" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case bristle = whisker.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 WHISKER mean?
WHISKER noun- That part of the beard which grows upon the sides of the face, usually of the male, or upon the chin, or upon both.
- A hair of the beard.
- One of the long, projecting hairs growing at the sides of the mouth of a cat, or other animal.
- The (very small) distance between two things.
- Spreaders from the bows to spread the bowsprit shrouds.
- A graphic element that shows the maxima and minima in a box plot.
- One who, or that which, whisks, or moves with a quick, sweeping motion.
- A small tendril that forms on metal.