To hide a group's administration from the list of group members:

1. click "Settings" under the group's profile picture;
2. in the menu to the left, select "Privacy settings";
3. in the "Administration settings" section, change the "Hide administration" option to "Yes"
4. confirm your selection by clicking "Save".

Now group members will not be able to see the administration of the group. Note that only the group administrator can change group settings.