尚 + 不 + 清楚 + Clause
清楚 (qīngchu) means "clear" or "to understand clearly." It can function as both an adjective meaning "clear" and a verb meaning "to know/understand." A common pattern is 不清楚, meaning "not clear" or "unclear." For example, 尚不清楚 means "it is not yet clear."
这件事的原因目前还不清楚。
Zhè jiàn shì de yuányīn mùqián hái bù qīngchǔ.
The cause of this matter is still unclear at present.
你能说清楚到底发生了什么吗?
Nǐ néng shuō qīngchǔ dàodǐ fāshēng le shénme ma?
Can you explain clearly what exactly happened?
我不太清楚他为什么突然辞职了。
Wǒ bú tài qīngchǔ tā wèishéme tūrán cízhí le.
I'm not very clear on why he suddenly resigned.