What does the cryptic crossword clue "Admonition, it seems, about breaking into song (12)" mean?

The wordplay uses an anagram. anagram of STISEME (synonym="STISEME") + CHANT (synonym="‘song’") = CHASTISEMENT The answer is CHASTISEMENT.

Admonition, it seems, about breaking into song (12)

Guardian Cryptic #29424 | 18 Across | 2024-07-02 flower