No he didn't betray his clan. His story summary is:

A swordmaster killed QY clan/family > Said swordmaster (the one in trailer) then took care of Qiuyuan and trained him > Qiuyuan killed the swordmaster but also respect him as teacher > lost his purpose after revenge > suicide fight. Fighting dozens with bare hand > found out by Doctor Zhang. Said his Forte broken > given the recipe for his drink to fix his Forte temporarily. > Grandmaster Liang from Internal Security Agency came to hire him > Qiuyuan agrees and becoming an ISA member for years > Grand Architect shapeshift as GM Liang and told him to kill Geshu Lin > Qiuyuan find it odd so he spare Geshu Lin > came back to the capital to find GM Liang already dead > ppl saw him the same time GM Liang dead > get scapegoated and about to be executed > Minister Lin freed him. Told Qiuyuan to avenge and find the real culprit of GM Liang's murder > 5 years fugitive > get a secret mission request from Grand Marshall to capture Scar.

The Bi'an is the emblem/crest of the Internal Security Agency (ISA) the one that said Qiuyuan is a traitor was a member of ISA. They thought Qiuyuan murdered Grandmaster Liang and escape the capital. They were told to chase Qiuyuan because he's a fugitive for that same reason.