1N-UNCOUNT 谷糠;麸皮Chaff is the outer part of grain such as wheat. It is removed before the grain is used as food. 谷糠;麸皮
2PHRASE 分清良莠;去芜存菁 If you separate the wheat from the chaff or sort the wheat from the chaff, you decide which people or things in a group are good or important and which are not. 分清良莠;去芜存菁
It isn't always easy to separate the wheat from the chaff.