How to Delete Items from a Playlist in iTunes
If you want to change up your iTunes playlists, you can delete items from playlists while still keeping them in your library. When you delete an item from a playlist, the item is simply deleted from the list — not from the library. You can also delete entire playlists and this also does not delete or change the content in the library. Note: Switch to the Library sections (Music, Movies, TV Shows, and so on) in the Source pane to delete items from your library.
To delete an item from a playlist, select the playlist in the Source pane and then select the item. Press Delete/Backspace or choose Edit→Delete. In the warning dialog that appears, click Remove to remove the selected item from the list.
You can also completely delete an item from your library from within a playlist by selecting the item and pressing Command+Option+Delete (Mac) or Ctrl+Alt+Backspace (Windows).
To delete a whole playlist, select the playlist in the Source pane and then press Delete/Backspace or choose Edit→Delete.