What does the cryptic crossword clue "City’s sexual stimulant knocking six out (4)" mean?

The definition is "City". The wordplay uses a deletion. AGRA (deletion) = AGRA; definition: "City's" The answer is AGRA.

City’s sexual stimulant knocking six out (4)

Guardian Cryptic #29334 | 14 Across | 2024-03-19 flower