The 22-year-old Belgium international is currently on loan with the Baggies from KAA Gent.
"Yassine was involved in all the goals," said Clarke. "He made two and scored one but he's a young player, who has a lot to learn.
"We will keep his feet on the ground and try to keep him level headed but you could see he has some assets and he can look exciting on the pitch.
"I'm keen to keep his feet on the ground. It's not a case of keeping him on a rein - we just need to make sure he develops at the right pace.
"I know a little bit about looking after young players and it's important that when they do play it's only when they're ready to play.
"What people saw yesterday might have excited them and it's good for his confidence, especially given that he's a winger who tends to thrive on confidence."