This rare kanji has no clear standalone meaning. Treat its meaning as uncertain.
鈼 combines 金 (metal) with 乍, which likely contributes the sound. The exact historical development is uncertain.
The left side is metal 金, and the right side 乍 looks like a saw or tool. Picture an old metal tool used for cutting or shaping, but its exact purpose is unclear.
For サク, imagine a sack of metal tools: sack -> サク, and the metal 金 part reminds you it's a metal tool.