In this story, the Zhao clan were a major military clan that served Dong Zhuo during the initial turmoil of the end of the Han era. The clan was inflitrated by two men. The first was Liaoyuan Huo, the Sima clan assassin and future Zhao Yun. He managed to get himself adopted as the son of the clan's head. The second was the Eighth Genius of Water Mirror who tried to impersonate the clan's blood heir Zhao Ang but got found out.
The Zhao clan was already mentioned in the first chapter as Liaoyuan Huo was only allowed to get close to Dong Zhuo's main advisor Xu Lin because everyone thought he was the loyal son of the loyal Zhao clan, Zhao Huo. This was how he assassinated Xu Lin. As a result of the assassination, the Zhao clan was purged by Xu Chu under orders from Dong Zhuo. This actually served Lu Bu's purpose as he was the one who hired Liaoyuan Huo to kill Xu Lin. The assassination deprived Dong Zhuo of both his advisor and his strongest supporters, the Zhao clan.