The teacher asked students to ask questions for further clarification.

clarification 是名词，来自动词 clarify（澄清、阐明），由形容词 clear（清楚的）加上动词后缀 -ify（使...化）构成，表示"使变得清楚"的动作。clarification 指"澄清、说明"的过程或结果。