What does the cryptic crossword clue "Express understands seedy nightspot’s sudden decline (8)" mean?

The definition is "decline". The wordplay uses a homophone (sounds like). Homophone of “knows” + DIVE (a seedy nightspot) The answer is NOSEDIVE.

Express understands seedy nightspot’s sudden decline (8)

Guardian Cryptic #29382 | 20 Across | 2024-05-14 flower