What does the cryptic crossword clue "After heated clashes with many, agree fixture for big match (4,3,3)" mean?

The wordplay uses an anagram. anagram of HEATED (synonym="… clashes") + MANY (synonym="After … with") = NAMETHEDAY The answer is NAMETHEDAY.

After heated clashes with many, agree fixture for big match (4,3,3)

Guardian Cryptic #29499 | 18 Across | 2024-09-27 flower