What does the cryptic crossword clue "Extinct bird mentioned in dreary lecture (5,3)" mean?

The definition is "Extinct bird". The wordplay uses a homophone (sounds like). Sounds like GREY TALK (‘dreary lecture’). The answer is GREATAUK.

Extinct bird mentioned in dreary lecture (5,3)

Guardian Cryptic #29095 | 12 Across | 2023-06-13 flower