The Wildcats faced a 35-31 halftime deficit, but a 3-point play by Chris Kelly, followed by Clemente's 3-pointer gave KSU a 68-56 lead with 4:37 left.
Clemente also sank 6-of-6 free throws, the last two with 19 seconds remaining.
Kelly and Jacob Pullen scored 15 points apiece, while adding a combined 11 rebounds for the Wildcats (19-4, 6-3), who have won two straight.
Craig Brackins paced Iowa State with 29 points and 12 rebounds.
Marquis Gilstrap scored 18 with eight rebounds and Diante Garrett added 10 points, three rebounds and five assists for the Cyclones (13-10, 2-7), who have lost five of six.
They shot just 36.1 percent.