The win - thanks to a late goal from Nikola Zigic at the Riverside - sent the Blues seven points clear of the Championship drop zone.
But Clark said: "We've still got to be aware of what's going on behind us.
"With the results teams are getting below us, there's more good runs in the bottom half of the table than the top, so it's turned on its head.
"If we do things right in the last eight games we'll see where that will take us, but that's two defeats in 14 games now, which is pleasing.
"We came here and did our jobs. We showed energy, pace and looked a real threat going forward. I'm delighted."