Definitions of supporter:

noun: a person who backs a politician or a team etc.
Example: "All their supporters came out for the game"
noun: a support for the genitals worn by men engaging in strenuous exercise
noun: a band (usually elastic) worn around the leg to hold up a stocking (or around the arm to hold up a sleeve)
noun: someone who supports or champions something
noun: a person who contributes to the fulfillment of a need or furtherance of an effort or purpose