The 21-year-old hitman fired in two goals as Wednesday drew 2-2 at Molineux earlier this season and will be used as a target man at Hillsborough.
For a player so young, he has already notched 80 championship appearances for the club who he left after graduating from their academy – and was their top scorer with five league goals to boot.
Clarke will challenge Steve MacLean, Marcus Tudgay and Deon Burton for a place in attack and will give The Owls some much-needed depth in the forward department – although his arrival could spell the end for David Graham and Barry Corr.
Clark will wear the number 18 shirt at Hillsborough and will be available for selection for Saturday's clash with