What does the cryptic crossword clue "Naughty fun is ultimately immoral and bad (6)" mean?

The definition is "Naughty". The wordplay uses an anagram. anagram of FUN IS L = SINFUL; definition: "Naughty" The answer is SINFUL.

Naughty fun is ultimately immoral and bad (6)

Times Cryptic #28731 | 12 Across | 2023-10-11 flower