is this data in a certain index? is there any other data in this index that you do not want to delete?
Then there really is no easyer way to do this. Using the | delete command would be the best choice, and once data rolls to frozen it will then completely get deleted.
Otherwise if you do not care for the data on a certain index you can use the ./splunk delete eventdata
(note, all data in that index will be removed).
To remove the file from being indexed again go to your manager page and head to:
Manager » Data inputs » Files & Directories
then disable the file that you do not want to index anymore.
Hope this helps,