Sage
Wise Person
A clever person is a sage or a wise person. This word has quite an old-fashioned feel, so you'll mostly see it in old stories!
けんじん
This is a jukugo word that uses the on'yomi readings of the kanji. You should be able to read this on your own.
あの教授、外では賢人って言われてるけど、実は内弁慶らしいぜ。
That professor is called a sage outside the home, but I heard he’s actually a braggart at home.