If you are talking about the Response time hotspots active wait time would be time in the request spent waiting, e.g. because Object.wait() was called.
Could you add a few more details on what exactly you mean? A screenshot would be nice.
Please see attached screenshot.
My answer above and Michaels comment apply to this.
If you click on the Actice wait time entry in the Top findings you will get a call breakdown and see which part of your code is actually causing the wait time.
The Response Time does not include asynchronous parts. So if some of the Wait Time is in an async operation, it can cause the difference in total time and response time.