Lightweight, Light, Light Weight
い adjective
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 lightweight? It's also lightweight.
かるい
The reading you learned with the kanji is the reading you'll be using here. Because of that, this word is kind of a lightweight.
このクッション、すごく軽いですね。
This cushion is very light.
毎日の朝ごはんは、フルーツやシリアルといった軽い物を食べています。
I eat light snacks such as fruits and cereal every day for breakfast
軽いエクササイズで、ストレスがなくなりました。
With some light exercise, my stress has disappeared.