This rare kanji has no clear standalone meaning. Treat its meaning as uncertain.
秢 combines 禾 (grain) with 令, which likely contributes the sound. The exact historical meaning is uncertain, and the character is rare in modern Japanese.
The left side 禾 suggests grain or a plant, and the right side 令 looks like a person kneeling under a roof. Imagine a rare grain that grows only in sheltered places, but its exact use is a mystery.
For レイ, picture a ray of sunlight hitting the rare grain: ray -> レイ, and the grain 秢 grows in that light.