WordNet sense 1 (customers collectively):

business, clientele

WordNet sense 2 (a communication that indicates lack of respect by patronizing the recipient):

condescension, disdain

WordNet sense 3 (the act of providing approval and support):

backing, backup, championship, championship

WordNet sense 4 (the business given to a commercial establishment by its customers):

trade

WordNet sense 5 (be a regular customer or client of):

patronize, support, patronise, keep going