The Blues looked set for victory until Kirk Broadfoot cancelled out Curtis Davies' opener, and Clark's men were denied an opportunity in the 87th minute when substitute Wade Elliott blazed over from six yards with the goal at his mercy.
A disappointed Clark said: "It was definitely (two points dropped), I think we deserved to win the game.
"It was a nervy start for the first 15-20 minutes but we grew into the game and finished the half really strong, we could have been more than one-nil up.
"And then we started the second half really well too, unfortunately we couldn't get that decisive second goal and then they score a very similar goal to us from a set-play.
"It's a bit frustrating really. We've played with a lot of desire, tenacity and at a high tempo."
Regarding Elliott's miss, Clark added: "I haven't seen a replay yet but one of the coaches has and it looks like it's bobbled up a bit."