Austin, signed from Burnley during the summer, scored from close range four minutes into the second half after Birmingham failed to deal with Joey Barton's free-kick.
Tom Adeyemi inadvertently sliced the ball against the underside of his own crossbar, giving Austin the simple task of tapping home.
Jordan said: "Charlie will score goals. His tally will be okay at the end of the season. He'll be hitting the net.
"I think he's been a bit unfortunate since he joined us. He got a goal very quickly against Exeter in the Capital One Cup and then had a number of games where he had chances, hit the bar and it didn't go in for him.
"I think it will give him a bit of relief and a bit of comfort getting a goal. And he played well - he was more involved in the second half than the first.
"In the games he's played he's had chances, he's just been unfortunate that his tally has not been more."
Birmingham were certainly unfortunate, having gone close to going ahead when Lee Novak's first-half header hit the post.
And the Blues felt they should have been awarded a late penalty after Jonathan Spector went down under a challenge from Richard Dunne.
Instead, the defender was booked for diving - summing up a frustrating day for Clark's side.
"I think we rode our luck a bit as Birmingham created opportunities," Jordan admitted.
"In our previous 1-0 wins we maybe could have got another goal but today I think the chances went to Birmingham. They failed to take them and we took our opportunity.
"But the team spirit is there and we want that to show in what is a very important period for us, with three games in a week."
Birmingham's defeat - their fourth in six matches - means the club have made their worst start to a league season for 25 years.
Blues manager Clark said: "I'm just frustrated for the players. It's cruel.
"In the first half we could have been 2-0 up. We then score an offside goal and 30 seconds later they get one from a set play. Then we still created opportunities, but it wasn't to be.
"It's tough for my young players. We've had some good performances but not got the results.
"I've told them to keep the belief, because we are playing well and we will get results.
"Playing with three centre-backs has made us really solid but I also wanted us to be positive and try to create opportunities and I think we did that."
He added: "I don't know whether it was a penalty. I'll need to have another look at that.
"I don't want to make myself look foolish by saying it's a penalty [and then seeing that it was not].
"All I'll say is that John Spector is a good lad - a great type and a great, honest professional."