The most common and most likely answer to this crossword clue is the 4 letter word CURS
I've seen this crossword clue in The Times
C
U
R
S
More clues leading to the result CURS
Buddy explains!

The straight part
We know that "Bad chaps" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case bad chaps = curs.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 CURS mean?
CURS noun- A contemptible or inferior dog.
- A detestable person.