A Sean McConville goal moved Stanley into fourth place in League One after they saw off second-placed Peterborough at London Road.
It's 29 games - a year - since the Reds lost once they have gone ahead and, after the winger put Stanley in front, they held on to record victory against Posh, who haven't won at home in four league games.
Stanley charged ahead in the 11th minute. Sam Finley played a superb ball to Offrande Zanzala at the far post and he headed it down into the danger area with McConville there to find space and fire home his sixth goal of the season.
They could have doubled their advantage almost immediately but former Reds stopper Aaron Chapman grabbed the ball at the second attempt after Nick Anderton's cross was met by the head of Clark.
Posh are top scorers in League One and, on 17 minutes, striker Matt Godden's dipping shot crashed against the crossbar.
Stanley continued to press with corners causing panic in the Peterborough penalty area - home defender Mark O'Hara almost scored an own goal, with his diving header into the side netting.
Jonny Maxted was making routine saves as Posh hunted for the equaliser while Chapman kept out a McConville free kick on the stroke of half-time.
Peterborough boss Steve Evans went into the referee's notebook just before the interval.
Jason Cummings tried his luck with headers twice early in the second half while, at the other end, Dan Barlaser's strike was deflected wide and McConville just couldn't quite reach a Finley ball in.
Cummings was a threat for the home side and, from a throw, he turned and his strike was inches from the top corner of the net.
There were half chances for both sides before, with six minutes to go, Godden had an opportunity to level it as he got on the end of a cross from Marcus Maddison but his effort raced just wide.
Sub Scott Brown almost made injury time easier for boss John Coleman but flashed an effort inches wide - the Reds, though, held on for victory.