From the resulting corner, Phil O'Donnell could only deflect Clarkson's driven cross wide from four yards out.
The 2 January tie was cancelled as a mark of respect following the death of Motherwell captain Phil O'Donnell.
All wore number 10 shirts to commemorate late captain Phil O'Donnell, who died from heart failure while playing in December.
The Swede will join up with other members of Celtic's 1998 league winning side to pay tribute to Phil O'Donnell, who died earlier this season.
CNN's Phil O'Sullivan and Schams Elwazer contributed to this report.
CNN: State TV: 4 dead after quake hits Iran, near nuclear site
Swift handling from Sam Tomkins, Sean O'Loughlin and Phil Bailey then put Richards away for his opener five minutes later.
The left wing gathered his own chip-ahead and stepped past O'Gara before offloading to the supporting Phil Godman, but the fly-half was thundered into touch by a retreating Brian O'Driscoll just a few metres short of the Irish line.
Other previous winners include Peter Kay, Dylan Moran, Lee Mack, Phil Kay, Tommy Tiernan and David O'Doherty.
"This is panic, this it isn't organized at all, " said Phil Streible, a senior commodities broker at RJ O'Brien Futures.
Alun-Wyn Jones won the race to start alongside captain Paul O'Connell in the second row with Phil Vickery and Gethin Jenkins to prop alongside England hooker Lee Mears.
Martyn Williams, Ronan O'Gara and Simon Shaw are all are on their third Lions tour, while Shane Williams, Andrew Sheridan and O'Connell, plus replacements Stephen Jones and Phil Vickery, are on their second.
"When we met with Phil we were inspired by his commitment to San Diego and his passion for the Padres, " Kevin O'Malley, one of the other potential investors, said in a prepared statement released to the PGA Tour's website.
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