1. 线索;提示
    A clue to a problem or mystery is something that helps you to find the answer to it.

clue的反义词

    e.g. Geneticists in Canada have discovered a clue to the puzzle of why our cells get old and die...
           加拿大的遗传学家已经发现了解开细胞衰老、死亡之谜的线索。
    e.g. How a man shaves may be a telling clue to his age.
           男人刮胡子的方式也许能泄露其年龄。

2. (破案)线索
    A clue is an object or piece of information that helps someone solve a crime.

clue的解释

    e.g. The vital clue to the killer's identity was his nickname, Peanuts.
           查明杀手身份的重要线索是他的外号叫“花生”。

3. (纵横填字游戏的)提示语，解答提示
    A clue in a crossword or game is information which is given to help you to find the answer to a question.

4. 不知道;一无所知
    If you haven't a clue about something, you do not know anything about it or you have no idea what to do about it.

    e.g. I haven't a clue what I'll give Carl for his birthday next year.
           我不知道明年卡尔过生日我该送什么。