This rare kanji has no clear standalone meaning. Treat its meaning as uncertain.
鎨 combines the metal radical 金 with 隼, but the exact historical development and original meaning are uncertain.
The metal radical 金 suggests something metallic, but without a known meaning, the character remains a mystery. Imagine a rare, unnamed metal object.
For シュン, picture a shiny metal piece that makes a 'shoon' sound when struck: shoon -> シュン.