This is similar to removing a Lead. Except for the fact that you may want to report on the leads lost. 

Hence you will only have to cancel the lead and not delete it. 

Select Jobs > Detailed Leads

Find the lead that needs to be removed and click on the lead number.

The left navigation panel will expand with all contract (lead) details.  The heading "Contract Details" will also gain focus.  

  1. Expand the Lead Number
  2. Select "Management" under the lead

The Action Pane will change its state to "Contract Management".  
Click on 'Change contract Status'. 

Choose Cancelled from the list and choose the appropriate reason. 

You can have pre populated drop down. This list can be created if you have the admin rights. 

else you can enter the reason under 'OtherReason:' section below. 

This will change the lead status to 'Lost' and will not be listed under the 'Detailed Leads section' however they can be searched (within ClickHome) and reported on as well.