Step 1: Go to the 'Drilldown' in the menu bar and select 'Client' in the block titled 'Partition by':

Step 2: Pick a visualization (for instance a list for financial data):

Result when selecting the List:

Step 3: Save the report for future use by clicking 'Save as new report' at the top of the page:

and give it a name:

Step 4: Go to 'Reports' in the menu bar to find the top client report: