Uncheck the "Label" property on the Dimensions tab. That will remove the arrow and the current fieldname display.
If you want to display the current fieldname, add a Text In Chart element with the expression:
and position it where you want.
Hi.. Its old post but just want to share workaround so it may be helpful for someone.
To remove the icon for drilldown group, create a variable and pass the group name in it. Now use variable in the dimension.Icon will not come but still drilldown will work.
Group Name: Commodity Group
Variable Name: vCGrp (Group name should be in definition)
Dimension: [$(vCGrp)] (Square bracket is used since group name has spaces.)