In this paper we propose a structure-based clustering technique that transforms a given graph into a specific double tree structure called multi-level outline tree. Each meta-node of the tree - that represents a subset of nodes - is itself hierarchically clustered. So, a meta-node is considered as a tree root of included clusters.The main originality of our approach is to account for the user focus in the clustering process to provide views from different perspectives. Multi-level outline trees are computed in linear time and easy to explore. We think that our technique is well suited to investigate various graphs like Web graphs or citation graphs.