This rare kanji has no clear standalone meaning. Treat its meaning as uncertain.
鐁 combines 金 (metal) with 斯, which likely contributes the sound. The exact historical development is uncertain.
The metal radical 金 suggests something related to metal, but the overall meaning is unclear. Imagine a mysterious metal tool whose name has been lost.
For シ, picture a sheet of metal: sheet -> シ, and the metal radical 金 reinforces the metal connection.