A business’s ~ is all its regular customers, considered as a group. (BUSINESS)
...Halifax’s ~ of 21 million people.
N-COUNT
CUSTOMER BASE
Meaning of CUSTOMER BASE in English
Collins COBUILD. Толковый словарь английского языка для изучающих язык Коллинз COBUILD (международная база данных языков Бирмингемского университета) . 2012