What does the cryptic crossword clue "Cat about to drink mixed gin joins the 25, perhaps (5,2)" mean?

The wordplay uses an anagram. anagram of IGN (synonym="IGN") + SSUP (synonym="SSUP") = SIGNSUP The answer is SIGNSUP.

Cat about to drink mixed gin joins the 25, perhaps (5,2)

Guardian Cryptic #29558 | 21 Across | 2024-12-05 flower