@feha that hand clap is not the plan. It's just a skill that Wolfe learned to incorporate to her fighting style. It wasn't intentionally created to be a part of this plan.
What's part of the plan is, taking Rachael there. She is a famous gorilla of a knight, so when she's there he knows that the assassins won't be able to just move in so casually and kill them all.
Now, the MC knows that the main targets of the assassins will be him and Lacra so he bait them into attacking by making Rachael left her position and purposely dropped the book. And when they attack, Rachael can immediately return and counter them because, as she said, the targets and the timing of the attack is known to her. Lacra's barrier is also part of the plan.
After that, it's a fight between the assassins and the two bodyguards. More of the plan should be revealed next chapter, because MC's aim is not the assassins, but the mastermind behind them.
Oh and by the way, that assassin who fought Wolfe didn't know she was going to clap. He thought she was going to thrust her palm forward, thus he thought it's going to be a palm attack. So that means that her clap is not a common skill often used in battle.