How to deal with a student lacking commitment
First of all, people are not mind readers; so first tell the student that he/she needs to work harder. and then: 

Longer Time Intervals: This worked for me for number of students. Basically double the time intervals between meetings. So for example, if you meet the student every week, tell him/her that his/her progress is not satisfactory so meet me in two weeks time and tell me what you did.

Warning With a Help of a Senior: Then give a warning for the next time interval, and tell the student if he/she keep working like this, you will not support him/her anymore. For this, it is better to have a senior lecturer (e.g., head of a group) in the meeting as well. 

Refuse of Support With a Help of a Senior: Then, if the student progress is not satisfactory, have another meeting with the student and with the help of a senior lecturer let the student know that you did you best and because of the student's lack of progress you are not willing to work with him/her anymore. So, he student needs to find another supervisor to work with him/her.