This rare kanji has no clear standalone meaning. Treat its meaning as uncertain.
醻 combines 酉 (sake jar) with 壽, which likely contributes the sound. The exact historical development is uncertain.
The left side is a sake jar 酉, and the right side 壽 suggests long life. Picture a ceremonial toast with sake, but the exact meaning is unclear.
For シュウ, imagine a long-lived person named Shuu pouring sake from the jar: Shuu -> シュウ.