This rare kanji has no clear standalone meaning. Treat its meaning as uncertain.
The exact historical development of 靕 is uncertain. It visually combines 正 and 青, but no clear traditional etymology is available.
With no clear meaning, picture 正 (correct) and 青 (blue/green) side by side as an abstract symbol of something pure and right, but remember its meaning is uncertain.
For シン, imagine a shin (shin) guard that is both correct (正) and blue (青): shin -> シン.