Clever
Intelligent
This is a single kanji with an い on the end, meaning you know it's probably an adjective. What's the adjective form of clever? It's clever or intelligent.
かしこい
If you're clever enough, you can start up an awesome company that makes tons of cash. A cash co (かしこ).
僕はあまり賢くはないけど、やるときはちゃんとやってみせるよ。
I’m not too clever, but I have my moments.