Sentence:  In his teens O ' Banion was enrolled in the vicious Market Street gang and he became a singing waiter in McGovern's Cafe , a notoriously low and rowdy dive in North Clark Street , where befuddled customers were methodically looted of their money by the singing <WSD>waiters</WSD> before being thrown out . 
Meaning of the word marked with <WSD> tags:  a person whose occupation is to serve at table (as in a restaurant)