According to the Cambridge Dictionary, one of the many definitions of "Cluster" is a group of people that share a common knowledge discipline, social or familiar bonds. Actually, that wodr became trendy to define a "bubble" that's composed by a group up to 10 people. The people who already belong to a cluster cannot be transfered or move by their own will to another one. However, the meaning of clusters can be misunderstood and can lead to become social groups for ALL purposes, including throwing clandestine bashes leading to a rise of infected patients during the lockdown. Something that concerns Sugar and her duty in the Medical Brigade, and must be told to her trainee.