This rare kanji has no clear standalone meaning. Treat its meaning as uncertain.
鎀 combines the metal radical 金 with 修, which likely contributes the sound. The exact historical development and original meaning are uncertain.
The metal radical 金 suggests something related to metal, but the overall meaning is unclear. Think of it as a mysterious metal object whose purpose is unknown.
For シュウ, imagine a shoe made of metal: shoe -> シュウ, and the metal radical 金 reinforces the metallic image.