When I go to the beach, sunscreen is essential.
What do you think would be essential to becoming fluent in Japanese?
Tasty bacon is indispensable in promoting efficient work.
It's not possible to lack. It is indispensable and essential, so don't lack it!
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.