organization formed mainly by traders and manufacturers to cater for the interest of their members is

A trade association

Explanation:

A trade association is an organization or a group founded by businesses in the same industry. A trade association is created to assist in coordinating activities that improve the welfare of its members.  By uniting in an association, firms can lobby for a better business environment from the government.

A trade association allows members to bond and network. It presents an opportunity for members to strategize and exchange important business information.

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