The investigation found no evidence against him, so he is officially in the clear.

in 是介词，表示"处于某种状态"。 the 是定冠词，这里特指某种状态。 clear 是形容词，意思是"清楚的、清白的"。 in the clear 是一个固定短语，意思是"无罪、清白"，表示某人没有嫌疑或责任。