The most common and most likely answer to this crossword clue is the 7 letter word SADISTS
I've seen this crossword clue in The Daily Telegraph
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More clues leading to the result SADISTS
- They enjoy inflicting pain, like retired detectives way back
- Unhappy is good person about perverted types
- Cruel people with unhappy lives crossing street
- Island sin sites regularly chosen by deviants
- Brutes assisted in revolt after European departs
- Down is way back for such cruel people
- Thugs at first said to be mixed up in Nazi group — this is the kind of people they are
- Depressed by first leisure centre for cruel people
- Perverts and drips oddly included in school tests
- Perverts unhappy with first and second
Buddy explains!

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 SADISTS mean?
SADISTS noun- One who derives pleasure through cruelty or pain to others.