What does the cryptic crossword clue "Controversial ad alarms sea port in Africa (3,2,6)" mean?

The wordplay uses an anagram. anagram of AD + ALARMS + SEA = DARESSALAAM The answer is DARESSALAAM.

Controversial ad alarms sea port in Africa (3,2,6)

Daily Mail Cryptic #16666 | 12 Across | 2021-09-17 flower