If something is unclear, it is not known or not certain.
It is unclear how much popular support they have among the island's population.
不知道该岛上有多少居民支持他们。
Just what the soldier was doing there is unclear.
不知道那个士兵到底在那儿干什么。
If you are unclear about something, you do not understand it well or are not sure about it.
He is still unclear about his own future.
他仍然不确定自己的未来会怎样。