LSU (2-1, 0-1 Southeastern Conference) jumped out to a 7-0 lead in the first quarter when quarterback Rohan Davey found freshman wide receiver Michael Clayton wide open for a 67-yard scoring play on the Tigers' second possession of the game.
Tennessee (3-0, 1-0) did not have an immediate answer to LSU's big play but did get two first half field goals, from 44 and 42 yards, from Alex Walls to make the score 7-6 at halftime.
Clausen put the Vols ahead on their first possession of the second half with a touchdown on a successful quarterback draw from three yards out. The score culminated a 16-play, 82-yard drive that took 7:30 off the clock. A two-point conversion failed.
Clausen, who finished 18-of-38 for 309 yards, connected with Washington on the Tennessee's next drive. Walls extra point put the Vols ahead 19-7.
LSU managed just 19 yards of offense in the third quarter and punted on both of its possessions.
Travis Stephens scored the final Tennessee touchdown on a 1-yard plunge with 11:46 left in the game.
Davey, who was the driving force in the Tigers' 38-31 overtime win over Tennessee last season, finally sparked his offense in the fourth quarter. He led LSU on a six-play, 75-yard scoring drive that took just 1:15. The touchdown came on a 30-yard pass from Davey to Josh Reed with 10:13 on the clock. The same duo hooked up for a two-point conversion to make the score 26-15.
LSU had to settle for a 25-yard John Corbello field goal on its next possession, drawing the Tigers with eight points of Tennessee with 3:12 remaining.
The Volunteers ate more time off the clock and punted the ball over to LSU with 30 seconds to go in the game. Davey, who finished 21-of-43 for 356 yards, took the Tigers to the UT 40 in the closing seconds, but his desperation throw downfield fell to the end zone to end the game.
(3-0) Tennessee 26
(2-1) LSU 18 Final
LSU - MICHAEL CLAYTON 67 YD TD PASS FROM ROHAN DAVEY (JOHN CORBELLO KICK), 10:29
TENNESSEE - ALEX WALLS 42 YD FG, 13:55
TENNESSEE - ALEX WALLS 44 YD FG, 5:31
TENNESSEE - CASEY CLAUSEN 3 YD TD RUN (TWO-POINT CONVERSION FAILED), 7:30
TENNESSEE - KELLEY WASHINGTON 70 YD TD PASS FROM CASEY CLAUSEN (ALEX WALLS KICK), 2:32
TENNESSEE - TRAVIS STEPHENS 1 TD YD RUN (ALEX WALLS KICK), 11:46
LSU - JOSH REED 30 YD PASS FROM ROHAN DAVEY (JOSH REED RECEPTION FOR TWO-POINT CONVERSION), 10:13
LSU - JOHN CORBELLO 25 YD FG, 3:12