The failure was a real shake-up that made him start taking his job seriously.

shake-up 是由动词 shake（摇动、震动）和副词 up（向上）组成的复合名词，字面意思是"剧烈摇动"，引申为"重大变革"或"警醒"。 在这个句子中，shake-up 指"令人警醒的事件"，强调这次失败对他产生了强烈的冲击和警示作用。