The Hearts defender marked his first appearance for his country in three years with the opening goal before Che Adams sealed a memorable victory which boosts Scotland’s hopes of reaching the 2022 World Cup finals in Qatar.
Souttar has emerged from a spell of career-threatening injuries to reclaim his place in the squad and Clarke was happy to single him out for praise on a night when his team had no failures.
“John Souttar can be the story of the night for me,” said Clarke. “To come back from the injuries John has had over such a prolonged period of time, it was a bonus just to get in the squad. I know how happy he was to get the chance to play tonight.
“The way he played, the goal was the icing on the cake for him. His performance was outstanding. Congratulations to John. I gave him a big hug when he came off the pitch.
“I was quite emotional. You understand when you’ve been a player yourself and been involved in the game for so long, how difficult it is on the road back. I’m absolutely delighted for John.”
The victory means Scotland will be at home in their play-off semi-final on March 24 or 25 next year. Their seeded status means they already know they will avoid Italy, Portugal, Russia and, almost certainly, Sweden in that opening game.
Possible opponents include North Macedonia and Austria who could be joined by Finland, Turkey and Czech Republic.
The list will be completed after Tuesday night’s last round of group games when either Wales or Poland are most likely to seal a seeded spot.
Home advantage for the unseeded play-off final ties on March 28 and 29 will be determined by the outcome of the draw which takes place at Fifa headquarters in Zurich on November 26.
To complete a perfect night for Clarke, none of his players who were on the verge of picking up a suspension which would have ruled them out of the play-off semi-final were booked.
“We knew coming into it we were in a good place,” he said. “We wanted to put on a good performance to finish what has been a good campaign. We managed to do that in front of another fantastic Hampden crowd. It was a good night for everybody.
“We felt it was important for us to try and get the win which would secure the home play-off in the first match.
“We have to wait for the draw and see who we get. But it’s six wins in a row. Unfortunately for me we now go into a long four month winter hibernation.
“But it means everyone can come back here in March in a good frame of mind. If the team can pick up where they’ve left off, then they’ll be okay.”