Loose
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 loose? It's loose.
ゆるい
The reading is the one you learned with the kanji, so feel nice and loose and move on to the next item.
このシャツは首回りが緩いんですよね。
The neck of this shirt is pretty loose.