Posts in the Extra Theme are followed by a “sharing” section which lets users easily share your posts to the main social networks. As you see from the image above, these icons are preceded by the text “Share:”. If you’d like to remove this text (but leave the icons themselves), you can use the following CSS:
To add the CSS code to Extra, paste it into Extra's custom CSS box, which you can find from your WordPress admin menu at "Extra > Theme Settings > General > Custom CSS". Paste it after any other code already in there.