“Galvin cleaned the bases of the two men on them, by a long fly over the left field fence.” “Loose Fielding: The Buffaloes and Rochesters Yesterday–Other Ball News,” Buffalo Express, September 3, 1878, p4
Previous earliest use (Dickson Baseball Dictionary, 3rd edition, 2009):
1910. (New York Tribune, July 3; Edward J. Nichols).
Earlier Use to Mean Cleaning the Bases of Runners by the Fielding Team
“Cuthy to first on a safe hit to left, but on Clapp’s hit to short a double play cleaned the bases.” “Boston Bounced,” St. Louis Globe-Democrat, June 15, 1876, p3.