You can set up a default Clearing Profile as part of a Manual Allocation Profile. If you are selecting an Allocation, the Clearing Profile will not be active. You must either have the Manual Allocation selected in Global Configuration as the specified default, or you must select the Manual Allocation radio button from the Advisor tab of the Order Ticket on a per order basis.
The steps to define a default Clearing Profile can be found in the Interactive Brokers Users Guide.