Davis Keillor-Dunn rescued a point for Stags with a cool 90th minute finish from Aden Flint’s knockdown.
But Clough felt his side had got away with it after a below-par display.
“I am not sure how we got a point. I don’t think we deserved anything,” he said.
“I didn't think we did anything that we have been doing in the first 90 games nearly as good..
“We didn't hurt them in the final third in the first half, we gave the ball away, didn’t cross properly and the goal summed it up after we gave the ball away. We shouldn't be conceding from that position.
“I don’t know where it came from, there seemed to be a lot of poor decision making out there today.
“The only consolation is to stay unbeaten and get that point. It is the only bright point.”
“We are trying not to let performances like this happen,,You have to give the opposition credit with how they played but you have to be patient to open them up.
“To stay unbeaten after that performance is important.”
Inside the opening minute the U’s went close when Jayden Fevrier let fly, only to see his effort blocked.
The Stags replied with Louis Reed firing narrowly over the top following some neat approach play by Hiram Boateng.
As the lively start continued, Stags’ Lucas Akins tried a curling strike which drifted just the wrong side of the post.
As the Stags continued to press for an opener, defender Aden Flint eased forward before drilling a shot from distance narrowly over the top.
Just when a Stags opener was looking the most likely, the U’s opened the scoring after half-an-hour.
Joe Taylor slotted neatly past Christy Pym following Arthur Read’s tee-up.
Samson Tovide came close to doubling the hosts’ leading before the break.
Keillor-Dunn came close with the Stags’ first opportunity of the second period, though he ought to have done better when shooting straight at the keeper.
Keillor-Dunn then found himself presented with another great chance from Jordan Bowery’s cross, but he headed over the top from just eight yards.
However, Keillor-Dunn came to the rescue in dramatic style.