thin kimono, embroidery
袗 centers on a thin, lightweight kimono, often associated with delicate embroidery or fine decorative work on the garment.
袗 combines 衤 (clothing) with 㐱, which likely contributes the sound. The exact historical development of 㐱 is uncertain, but the character as a whole points to a type of garment.
The left side 衤 is clothing, and the right side 㐱 looks like fine, detailed lines. Picture a thin kimono decorated with delicate embroidery stitches.
For シン, imagine the thin kimono is so sheer that you can see the shin (skin) through it: shin -> シン.