I don’t have enough change.
Due to the lack of funds, the project that the central government planned was suspended.
You are fired because you lack experience and are always sleep deprived.
You have something that's not sufficient. When something isn't sufficient, you have a shortage. Keep in mind that this is a physical shortage, not a shortage of mental ability or something like that. To remember this, just think about how 足 also means "foot." What is a foot? Something physical. That's why this is a physical shortage.
This is a jukugo word, which usually means on'yomi readings from the kanji. If you know the readings of your kanji you'll know how to read this as well.