This rare kanji has no clear standalone meaning. Treat its meaning as uncertain.
貐 combines 豸 (beast) with 俞, but the exact historical development is uncertain. It may have originally referred to a type of animal, but the modern meaning is unclear.
The left side 豸 suggests a beast, and the right side 俞 looks like a creature with a shell and legs. Imagine a mysterious beast whose name has been lost to time.
For ユ, imagine a beast so rare that you are the only one who has seen it: you -> ユ, and the beast 貐 is your secret discovery.