The CORBA Trading Service is an object service advertiser for heterogeneous distributed computing environments. Current approaches for the design and implementation of such a CORBA service do not deal with some of the major problems of searching service offers in large scale distributed systems, that is performance and scalability problems. This paper proposes an appropriate approach for clustering service offers based on the service properties, in order to enhance the efficiency of the trading service. The proposed approach clusters service offers within a hierarchy of contexts by specialisation of property sets. Performance results of the proposed clustering approach is given and the benefits of including clustering of properties with the CORBA Trading Service are shown.