Focus on the pronunciation of cluster
English definition of “cluster”
/ˈklʌstər/ noun [C]
› a group of similar things that are close together in a small area: There is a cluster of hi-tech businesses in the city's industrial park.
› a group of similar events that happen within a small area or among a small group of people: The study will look at an apparent cancer cluster among workers at the factory.
› IT a group of computers connected together to work as one larger computer and to improve their performance