The world's official clock is kept on time through the second-by-second rhythms of a never-ending tennis game in a subterranean cavern below Greenwich. Harness the back-and-forth power of the sport for your own purposes with today's Groupon: for $45, you get a private tennis lesson at the Kingsbury Club (a $93 value), located in Medfield.

The Kingsbury Club, a multi-purpose health facility with a restaurant and multiple fitness/athletics options, ups the net worth of humankind with tennis programs for both raw and rehearsed racketeers. With the one-hour private tennis lesson ($78), taught by a certified senior tennis professional, and a one-day guest admittance ($15) to the Kingsbury Club, guests will refine backhands, polish up volleys, and learn how to properly grunt in spite of headband-wrought cranial pressure. The instructor will offer tips and suggestions on techniques and skills, helping students polish giant-scale ping-pong ability in time for summer's street-corner tennis showdowns.

Lessons are conducted at the Kingsbury Club's top-tier tennis facilities, with four hard courts and indirect lighting absorbing the cavernous echo accompanying each pop of racket-meets-ball or ball-meets-elbow. Get your tennis tuxedo tailored and visit the Kingsbury Club to energize the dormant Andre Agassi dwelling within.