1. have a clue
释义：To have a hint about someone or something，to know anything about something（了解，知道）
用法：要表示了解，知道某人或者某事，在短语后用介词about，即：have a clue about something or someone。
e.g. I don't have a clue about where to start looking for Jim.
e.g. Why do you think I have a clue about Tom's disappearance?
e.g. Maybe your boss just doesn't have a clue about how much you're really doing.
e.g. A: Do you think Paul suspects that we're having a surprise party for him?
B: No, he doesn't have a clue!
2. have a lock on
释义：To have complete control over someone or something. （对……胜券在握，完全控制……）
用法：介词on后面可以接somebody，即：have a lock on somebody（完全控制某人），也可以接something，即：have a lock on something（对某事胜券在握）。
e.g. Greg may think he has a lock on the promotion, but I'm determined to prove him wrong.
e.g. He would sooner see the whole bank go down the drain than get beaten by us. Unless we have a lock on him—and that won't be easy.
3. have a prayer
释义：To have any chance at all of doing or achieving something. （有希望，有机会）
e.g. With that giant supermarket opening up across the street, our little grocery store won't have a prayer of staying open.
e.g. You think you can beat me? Ha! You don't have a prayer.