The Saints came into the tie as underdogs, but produced an excellent performance as substitute Serge Atakayi’s strike on 87 minutes sealed their first away win in Europe since 2009.
The Inchicore side will take the victory back to Tallaght Stadium for the second-leg next Thursday, as they look to make the play-off stage against either Brøndby of Denmark or Basel of Switzerland, as well as a cheque for €1 million.
“It was a very good defensive, and disciplined performance,” said Clancy after the win.
“We had a few bookings early in the game which I thought were very soft, we seemed to be getting penalised for every contact and getting booked for very little. The opposition were not really getting booked for any tackles or pushes.
“We defended resolutely, and stuck to the game plan to frustrate them and limit them. How we dealt with crosses was excellent and still had a threat on the counter-attack. In the last couple of week’s we’ve left back-passes short, so it was good tonight we were on the other end of it."
Atakayi was also pleased, as he wrote his name into the St Pat’s history books with his first goal for the club. “I have worked very hard since I've come here,” he said. “I’m very happy to score. Everytime you play football, if you get a chance you have to take it. That’s how football is.”
Meanwhile, Stephen Bradley praised his Shamrock Rovers side for showing a killer instinct at the crunch to put the Hoops in control of their group stage football destiny.
Gary O'Neill's 96th-minute strike against ten-man Shkupi of North Macedonia gave the Hoops a 3-1 lead they will bring to Skopje for next Tuesday's decider.
If they progress through the Europa League third round qualifier, Rovers will be guaranteed group stage football via the Europa Conference League - and a €3.3m cheque from UEFA - and will have a chance to make the Europa League equivalent.
Bradley's side led two nil at the break, and he was frustrated that his team 'let their foot off the gas' to allow Shkupi back into it with a stunning effort from Queven halving the lead.
However, after withstanding a period of pressure, the Hoops pressed on when visiting midfielder Walid Hamidi received a second yellow and O'Neill's late strike followed a period of pressure.
"The goal at the end could be really important for us," said Bradley. "I'm slightly frustrated with our play in parts as it was sloppy and let them get a foothold.
"They showed they could score in the second half and we're in for a right game next week. But we felt we needed to go for it (after the red card) rather than take the 2-1. It's a great strike from Gary."