It sounds like each cluster has one parent cluster, but can have multiple children, which can either be nodes or additional clusters. And you want to find a term to refer to not only the direct parent cluster of the node, but all the rest of the parent clusters, all the way up the chain.
If this is the case, it's just a standard tree data structure. You should probably call it that and use the standard terminology for trees: use node instead of cluster, and use leaf for nodes without any children. This way anyone familiar with data trees can understand what you are talking about.
To describe a leaf and all of its ancestors use path (the sequence of nodes and edges connecting a node with a descendant). So you could talk about "the path to Node X", etc.
Note that trees have some restrictions (for example, they can't loop back on themselves) so please make sure your data structure doesn't violate any of these. There are other names for these kind of data structures.
FYI, HTML (or, more generically, XML) is one example of this kind of tree structure, and is represented as such in the Document Object Model (DOM).