When you see something as sweet, you're just looking at it like it's some little sweet kid with sweet flavoring. You are not taking it seriously, or you are taking it lightly. So sweet! That's why this word is to not take seriously or to take lightly.
The reading comes from 甘い and 見る. Don't take this word lightly and you should be able to learn it no problem.
Tuck in your shirt or your client may not take you seriously.