This rare kanji has no clear standalone meaning. Treat its meaning as uncertain.
縧 combines 糸 (thread) with 條, which likely contributes sound. The exact historical development is uncertain.
The left side is thread 糸, and the right side 條 suggests a long strip. Picture a long, narrow braided cord or ribbon, which fits the kun reading さなだ (braided cord).
For ジュウ, imagine a jeweler carefully braiding a precious thread cord: jew -> ジュウ, and the thread 糸 becomes a fine braid.