Problem:  For example material C_MATNR2, when we display key of the material on Analysis, it will display source system/12345 eg. WP1_400/11818.

In order to hide the source system, we can do following step:

1. Add the "source system" into the report. 
   
   
2. It will remove the key of material column already.
   
3. In case, "source system" does not required. It can be hidden by developer at query level (query designer) to select display as "No Display". 
   However, it is not recommend to hide it since the data may be misleading in case if the report has different source system in this example.