This rare kanji has no clear standalone meaning. Treat its meaning as uncertain.
鐯 combines 金 (metal) with 著, but the exact historical development and original meaning are uncertain.
The left side 金 suggests metal, and the right side 著 looks like a plant growing. Without a clear meaning, picture a mysterious metal tool used for digging or planting.
For シャク, imagine a metal shovel (shak) digging into the earth: shak -> シャク, and the metal tool 鐯 is used for heavy work.