Client (8)
I believe the answer is:
customer
'client' is the definition.
(I know that client can be written as customer)
This is the entire clue.
(Other definitions for customer that I've seen before include "Shopper (or now rail passenger!)" , "Someone who pays for goods or services" , "'Buyer, client (8)'" , "The person who is said in business to be always right" , "Person paying for item or service" .)