Go to Projects / Dialer Master, and highlight the queue you want to clear. Then click the Clear Queue button.
Please note that if calls have already been made on a project, apart from test calls, dropping the data from the project in the dashboard / Campaign Data. Once the records are dropped, the report and other associated things with completed data will be gone. You will still have the call logs under Project / Logs / Call logs.
It’s recommended to create a new project and copy script but not the data if you want to replicate a project with new data.