Clark and Wes Hoolahan both netted their first ever international goals to overcome a slow start and secure a comfortable victory, and the Aston Villa man says the squad can take pride from the result.
"We defended well from the start," Clark told BBC Sport.
"They looked the dominant side [in the first half] but we weathered the storm. We can take confidence from that.
"We've got a couple of important games coming up and we've got a good base to work on."
Norwich man Hoolahan, making only his third appearance for Ireland, was thrilled with his 76th-minute strike, and now hopes to give boss Giovanni Trapattoni a selection headache going into the qualifiers.
"To score for my country is probably one of the proudest things I've done," said the 30 year-old midfielder.
"The boys defended brilliantly in the first half and Ciaran came up with an important goal.
"All I can do is do my best when I'm called upon and hopefully tonight proved what I can do. I don't know?"
Trapattoni has, however, hinted that he will stick a more recognisable squad for the double header against Sweden and Austria.
"We have no need to change many, many players," said the Italian.