*Missable* To make sure you can obtain this trophy you must be sure to interact with the "Numbers" on the right side of the bar while rescuing Arthur from the goons early on in the game. These are needed in order to continue on the short path to this trophy.
Inside the speakeasy after Matches shows Kid a stick of dynamite, you will see Kid take a secret passage. After he does, head over to the Croupier and talk to him. Select the choice: "Bet on 7, 23, & 30". (Be sure to scroll to the bottom of the choices so you don't miss it. If you did not check the numbers located behind the bar when rescuing Artie at the beginning this option will not appear.)
This will open up a secret passage which gets you a shiny trophy and takes you to the barber shop outside. Please see the "Kid Restraint" trophy for a walkthrough.
*Important Note* There are reports of the option "Bet on 7, 23, & 30" not showing up for people even after examining the numbers and seeing Kid use the passage. If you know you interacted with the numbers at the beginning and you saw Kid use the passage, but you are unable to bet on those numbers then I suggest starting a new game and trying again.