This rare kanji has no clear standalone meaning. Treat its meaning as uncertain.
The exact historical development of 髿 is uncertain. It combines the hair component 髟 with 沙, but the original semantic or phonetic role of 沙 is unclear.
The top 髟 suggests hair, and the bottom 沙 suggests sand. Imagine hair as fine as grains of sand, but since the meaning is uncertain, treat this as a visual mnemonic only.
For サ, picture sand (さ) slipping through fine hair: さ -> サ, and the sand-like hair helps recall the reading.