The most common and most likely answer to this crossword clue is the 5 letter word SICKO
I've seen this crossword clue in The Guardian
S
I
C
K
O
More clues leading to the result SICKO
- Sadistic sort disgusted by love
- He's twisted thus by decisive blow
- Thus floor a perverted person
- Oscar-winning Kevin Costner for starters is backing Michael Moore film
- So knock out American deviant
- So good around pervert
- Perverted second-in-command, previously excellent
- Thus described, Headless Nick’s a pervert
- Frenzied, I sock a pervert
- Oddball so normal in retrospect
Buddy explains!

The straight part
We know that "perverted person" is the straight/definition part of the clue. The straight part is often a synonym or definition, in this case perverted person = sicko.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 SICKO mean?
SICKO noun- A person with unpleasant tastes, views or habits.
- A mentally ill person.
- A physically ill person.
- Characterized by depraved tastes or habits; deviant.