What does the cryptic crossword clue "'Restricted flight area manager' used as trivia (8)" mean?

The definition is "'Restricted flight". The wordplay uses an anagram. anagram of AS TRIVIA = AVIARIST The answer is AVIARIST.

'Restricted flight area manager' used as trivia (8)

Guardian Cryptic #29143 | 4 Down | 2023-08-08 flower