This rare kanji has no clear standalone meaning. Treat its meaning as uncertain.
僐 combines 亻 (person) with 善, which likely contributes the sound. The exact historical development and original meaning are uncertain.
A person 亻 beside 善 (good, virtuous) suggests a person of good character, but the actual meaning is unclear.
For セン, imagine a person 亻 who is so good 善 that they are called a saint: saint -> セン.