crepe, crape, wrinkles, creases
縐 centers on a textured, puckered surface in fabric: crepe or crape cloth, and by extension wrinkles or creases in any material.
縐 combines 糸 (thread) with 芻, which likely contributes the sound and may relate to a gathered or puckered texture. The exact historical development of 芻 in this character is uncertain.
The left side is thread 糸, and the right side 芻 looks like a bundle of gathered grass or hay. Picture thread being pulled tight around a bundle, creating wrinkles and creases like crepe fabric.
For シュウ, imagine a wrinkled shirt you need to iron: 'shoe' the wrinkles away, but since 'shoe' sounds like シュー, think of a shoe-shaped iron pressing out the creases, and the sound 'shoe' cues シュウ.