This word takes the reason meaning of the kanji, making it reason. What's the reason for it having two meanings? I have no clue, but there must be a reason.

While 理由 is the general term for reasons, 訳 tends to be more focused on the underlying reason or cause of something. It's also used when explaining a situation or when there's an implied need to justify or clarify something.

Since this word is made up of a single kanji, it probably uses the kun'yomi reading. You didn't learn this reading, so here's a mnemonic to help you:

What's your reason to wake (わけ) up this morning? Think about it. Now think of your reason to wake up tomorrow. What is it?