Now try to get this straight: there is nothing between us.

（はっきりさせておこう。僕らの間には何もない。）
　映画「雨に唄えば[Singin' in the Rain]」より。本当は恋愛関係にないのにゴシップ記事を鵜呑みにして自分はドンの恋人だと思い込んでいるリナ。ドンは彼女にこう言い聞かせる。

• "get something straight"＝「 しっかりと理解する／はっきりさせる／ちゃんとさせる」（to understand something clearly／agreeing with what is true or what is stated to be true／to understand the facts of a situation and be able to tell them correctly／to make a situation clear; to make sure that you or somebody else understands the situation／to make sure that you completely understand a situation）という意味。これはずっと「ちゃんとさせる」くらいの意味で理解していて、実際それで合ってるんだけれど、せっかくセリフで出てきたので、ここいらで例文をしっかり押さえておこう。「聞いてわかる」から「使える」レベルにしたい。
• 信じられないことや、驚いたことなど、混乱していることを「まっすぐに」するイメージ。一番身近な日本語で言うと、「ちょっと整理しよう、整理させて」って感じかな。
  • Now get this straight. You're going to fail history.
  • Let me get this straight. I'm supposed to go there in the morning?
  • We have to have our stories straight or else the police will get suspicious.
  • Let me get this straight [=I am surprised/confused by what you are saying and I want to be sure that I understand you correctly]: You want me to lend you $2,000?
  • You need to get your facts straight. [=you need to get your facts correct]
  • I wanted to get the facts straight.
  • Let me get this straight - Tom sold the car and gave you the money?
  • Let's get this straight―you really had no idea where he was?
  • Let me get this straight - am I paying for this?