This rare kanji has no clear standalone meaning. Treat its meaning as uncertain.
鈊 combines the metal radical 金 with 心, but its historical origin and meaning are uncertain.
The kanji has metal 金 on the left and heart 心 on the right, but without a clear meaning, it is hard to create a useful mnemonic.
For シン, imagine a shiny metal heart (金 + 心) that makes a soft 'shin' sound when tapped: shin -> シン.