Hi Saurabh,
You need not to add any code in system, there is already standard code in system for clear interaction event. You can find a standard component and view CRMCMP_IC_FRAME/HiddenView, you can keep breakpoint in do_handle_event and debug for more detail on working behaviour.
You need to add the Cancel button in correct toolbar profile. The toolbar profile is linked to the context are profile SPRO->interaction center web client->basic functions->Define context area profiles. Here the bsp components have been assigned to the profile id.
Please follow the below steps to identify the correct toolbar profile used in your business role.
SPRO->Customer relationship management->UI Framework->Business Roles->Define Business Role.. then select the interaction role which is using in your system.
After selecting the business role click on the Assign Function Profiles available at left side.
You could see a functin profile ID WBAR with profile value. The assigned profile value is your correct toolbar profile.
You can add the cancel button in toolbar profile and check in webui.
I hope this would be helpful for you.
Best Regards,
Dharmakasi.