Freshman designated hitter Zach Martinez drove in the winning run with a double in the bottom of the sixth inning and junior pitcher John Clerkin picked up the win in relief for Williamstown on a warm, windy afternoon on the Braves' field.
Senior centerfielder T.J. Dezzi was 2 for 2 with a pair of doubles and two walks for Clearview (3-1, 2-1).
"Our kids battled," Clearview coach Rocco Cornacchia said. "Their kids battled, too. It was a typical Tri-County Royal game."
Clearview took a 3-0 lead in the top of the first as Dezzi, a University of the Sciences recruit, and Jared Datz rapped doubles.
Williamstown battled back to take a 5-3 lead by scratching out a pair of runs in the first on one hit - a bunt single by Dan Musilli - and adding a three-spot in the fourth.
D'Alessandro delivered the big hit, a bases-loaded double on a 3-2 pitch.
"I had it in my head, 'He's going to throw it down the middle,' " D'Alessandro said. "He did and I was able to drive it."
D'Alessandro led off the bottom of the sixth with score tied at 5-5. "I knew somebody had to do it," he said.
He started the winning rally with another double. After Ross Micka's sacrifice bunt, Martinez chased D'Alessandro home with a double to right-center.
Ambrosius said D'Alessandro has stayed positive despite limited playing time.
"He's a terrific kid," Ambrosius said. "He comes to practice every day with a great attitude. He was huge for us today."
D'Alessandro said he never got frustrated waiting for his chance to make an impact at the varsity level. "I got reps on JV, a few reps on varsity," he said. "I knew I would get my chance."
Clearview 300 020 0 - 5 7 1
Williamstown 200 301 x - 6 9 0
WP: John Clerkin. LP: Kyle Slane.
2B: C-T.J. Dezzi 2, Jared Datz; W-Frank D'Alessandro 2, Zach Martinez. 3B: C-Eric Lauk.