Break, Vacation, Holiday
The kanji rest has a little hiragana attached, but it's nothing that would suggest it's anything but a noun (it is!). It means the same thing as the kanji, rest.
Since this word is made up of a single kanji with some hiragana, it should use the kun'yomi reading. When learning the kanji, you didn't learn that reading, so here's a mnemonic to help you with this word:
So, do you want a rest from work or school? You should say "Yes!" (やす).
There's no class today.
I go for drives with my dog on my days off.
When is your husband's day off?