When you are 'straight' with someone, you are honest with them, often risking offending them through criticism. Sometimes people will ask you to be straight with them, because people are often dishonest when they try to avoid upsetting people. Asking someone to be straight with you can often follow an argument, if you think the person you're arguing with is holding something back. You might hear this used in both social or professional contexts, and you can easily replace 'straight' with 'honest'; as in, 'to be honest with you'.

1. The best way to handle the situation with Rachel is just to be straight with her and tell her how you really feel.
2. The police accused Alex of lying in his statement, but he insists that he has been straight with them all along.

1. Being straight with you, I just don't think that you have what it takes to succeed in this business.