The most common and most likely answer to this crossword clue is the 8 letter word DASTARDS
I've seen this crossword clue in The Guardian
D
A
S
T
A
R
D
S
More clues leading to the result DASTARDS
Buddy explains!
The straight part
We know that "who are not nice people?" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case who are not nice people? = dastards.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 DASTARDS mean?
DASTARDS noun- A malicious coward; a dishonorable sneak.