How do I enforce an indemnity clause in an agreement between a consultant and his client.

The consultant signed a promissory note to a lender encumbering his corporate client without authorization and in violation of the consulting agreement. An action was brought by the lender against the corporate client for breach of contract when the promissory note was defaulted. The client, a Belize corporation, defaulted and a default judgment was issued. The lender wants to enforce the default judgment against the consultant based on the indemnity clause of the consulting agreement between the consultant and the corporate client that defaulted.