The Swans were bottom of the Premier League in January and looking doomed to relegation after sacking their second boss of the season.
But Clement's arrival as manager sparked a revival and, having collected 26 points out of a possible 54 under the former Bayern Munich and Chelsea assistant, they finished seven points clear of the drop zone in 15th.
Speaking to the Alan Brazl Sports Breakfast, ex-Swansea and Wales boss Toshack said: “Clement has done a terrific job at Swansea.
"The real test, of course, will come for him next season but he took over at the club when they were in a very, very difficult position.