For The Sake Of
For, In Order To, Due To
conjunction
This is sake paired with に, which suggests you're moving towards that "sake," like it's your purpose or reason for doing something. That's why this means for the sake of.
You'll see it in phrases like 友達の為にする (to do it for a friend), or 痩せる為に (in order to lose weight), where it'll often be written in kana. It can also be used without に, in short announcements showing the cause of something, like 雨天の為、中止 (canceled due to rain).
This uses a kun'yomi reading you didn't learn with the kanji, so here's a mnemonic to help you out:
For the sake of public safety, you will need to tame (ため) the wild beasts loose in our city. Now go — tame them, for everyone's sake!
あの人、ラーメンだけの為に日本まで行ったらしいよ。
Apparently, that person went all the way to Japan solely for ramen.
「君の為に言ってるんだよ！」が一番信用できないセリフだったりすると思わない？
Don't you think "I'm saying this for your own good!" is sometimes the least trustworthy line of all?
モテる為にギターと筋トレを始めたのに、結局いちばん話しかけてくるのはおじさんだ。
I started playing guitar and working out to get girls, but it turns out the people who come talk to me most are middle-aged dudes.
今日は夜勤の為に少し寝ておきたかったが、電車の音がうるさすぎた為、結局あまり眠れなかった。
I wanted to sleep a bit before my night shift today, but in the end I couldn't sleep much because the trains were too noisy.