What does the cryptic crossword clue "One among 6, 25 amalgamated, or what divides them (5)" mean?

The definition is "One among 6, 25 amalgamated, or what divides them". The wordplay uses a double definition. Double definition The answer is COMMA.

One among 6, 25 amalgamated, or what divides them (5)

Guardian Cryptic #29310 | 18 Across | 2024-02-20 flower