Liverpool midfielder Leighton Clarke has been sent off for the kind of challenge that would not have been out of place in a senior clash between the two bitter rivals.
And United striker Shola Shoretire also saw red after pushing Clarkson in reaction to the incident.
There was time for a late retaliation from United, who scored two more goals for a 5-3 final score that made the result closer than it had been for much of the game.
Clarkson gave Liverpool an early lead after being set up by Jack Bearne, who would go on to score two goals himself.
Ben Woodburn doubled his side’s advantage with a shot that deflected Di’Shon Bernard, before the Wales striker caught up with Bearne for the first of his goals.
Anthony Elanga reduced the deficit for United but Bearne scored again before Luis Longstaff scored to bring the score to 5-1 for the visitors.
Then came the Clarkson Farm Challenge which saw both sides downsizing for the past half hour.
Hannibal Mejbri and Charlie McCann scored late as United achieved some respectability in the 10v10 contest.
But it was too late to recover a result as treble legend Dwight Yorke watched from the bench, having recently worked with Neil Wood’s U23 squad.
United were missing several players who played for the U23s last season.
Teden Mengi is currently with Ole Gunnar Solskjaer’s first team, while James Garner, Dylan Levitt, Tahith Chong, Matej Kovar and Aliou Traoré are all on loan.
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Ethan Galbraith, Ethan Laird, Reece Devine and D’mani Mellor are all injured, while Angel Gomes and Largie Ramizani have both left the club.
Meanwhile, Barry Lewtas’ complete victory at Liverpool has shown that it is not just Jurgen Klopp’s first team that are at the top of their game at the moment, with many talented youngsters hoping to be a part of it. a bright future at Anfield.