WordNet sense 1 (a person who backs a politician or a team etc.):

admirer, booster, champion, friend, protagonist

WordNet sense 2 (someone who supports or champions something):

patron, sponsor

WordNet sense 3 (a person who contributes to the fulfillment of a need or furtherance of an effort or purpose):

assistant, help, helper

WordNet sense 4 (a band (usually elastic) worn around the leg to hold up a stocking (or around the arm to hold up a sleeve)):

garter

WordNet sense 5 (a support for the genitals worn by men engaging in strenuous exercise):

jockstrap, suspensor, athletic supporter