What does the cryptic crossword clue "Muscle that might make chins pert? Yes and no (9)" mean?

The definition is "Muscle". The wordplay uses an anagram. anagram of CHINS + PERT? = SPHINCTER; definition: "Muscle" The answer is SPHINCTER.

Muscle that might make chins pert? Yes and no (9)

Guardian Cryptic #29232 | 17 Across | 2023-11-20 flower