Step1:Go to the list or library that you want to delete a column from.
Step2:Or from a SharePoint site, select Settings Settings button from SharePoint Online , Site Contents, and then select the name of your list or library.
Step3:Select the column header for the column that you want to delete, and from the menu, select Column settings > Edit.
Step4:At the bottom of the Edit Column pane, select Delete.
Step5:To delete the column and the data in the column permanently, select Delete.