What does the cryptic crossword clue "Reference mark's ragged edges changed around (6)" mean?

The definition is "Reference mark's". The wordplay uses an anagram. anagram of RAGGED = DAGGER; definition: "Reference mark's" The answer is DAGGER.

Reference mark's ragged edges changed around (6)

Independent Cryptic #11867 | 31 Across | 2024-10-22 flower