Skipper Winston James scored a try hat-trick as Barnstaple overcame a hesitant start to beat Cleve 37-19 at Pottington Road.
Barum went behind twice in the first half and only led 20-19 coming up to the hour mark.
Two tries from Barum’s own Captain Fantastic, to add to one in the first half, plus a Luke Berry score ended any doubt about the result.
Victory puts second-placed Barum eight points clear of third-in-the-table Maidenhead in the race for the play-offs.
Devon rivals Ivybridge have slipped 12 points behind after they were beaten at Weston, which was their fourth defeat on the spin.
Jeremy Chugg, Barnstaple’s director of rugby, said Cleve had plenty to play for as they are scrapping to stay up and were a real handful for more than an hour.
“You think a struggling side away from home might not be at their strongest and will roll over easily – and that was not the case at all,” said Chugg.
“Cleve took their chances and defended well - and when there were only a couple of points in it we were a little worried.
“We have all played in or seen games like that won or lost by a couple of points either way and that is what you worry about.
“We were playing into the wind in the second half, never easy, and that made us play a with more control.
“It was not always pretty, but if winning ugly keeps us up there I will take it.”
Barnstaple took the lead on five minutes when Jake Murphy poked a penalty over.
Cleve did not wait long to reply as Max Baker ran through the centre to touch down. Nathan Huntley converted.
Barnstaple had not regrouped when Cleve scored again, this time after Huntley ran back an interception and added his own extras.
Twenty-six minutes had been played when Barum’s Adam Lloyd flopped over the line and Murphy’s conversion put them two points behind. A penalty put them ahead.
Two minutes before half time Barum opened up a 20-12 lead with a try from James that Murphy improved.
The second half got under way with Huntley claiming another interception try and leaving a point in it with the kick.
The next score was going to be crucial and it arrived on 55 minutes. Barnstaple got their driving game going and James finished off a 20-metre rumble with the try.
Cleve made Barnstaple wait for their bonus point that Berry scored with 10 minutes to go. Murphy added the extras.
James wrapped things up with three minutes to go with his third and Barum’s fifth try.
Barnstaple have no league game this Saturday.