This rare kanji has no clear standalone meaning. Treat its meaning as uncertain.
眒 combines 目 (eye) with 申, which likely contributes the sound. The exact historical development is uncertain.
The left side is an eye 目, and the right side is 申. Picture an eye wide open, staring intently, as if trying to see something clearly.
For シン, imagine a person named Shin staring with wide eyes: Shin -> シン, and the eye 目 is fixed on something.