The Championship promotion hopefuls recorded a 2-0 success at The Galpharm Stadium on Saturday afternoon.
"Today showed that the higher up the leagues you go all it takes is half a mistake and you get more and more heavily punished," Town boss Clark said after the match.
"I thought the team competed well, particularly in the second half. In the first half I thought we probably showed West Brom a bit too much respect.
"I told the players at half-time that they seemed to be treating the game more like a pre-season friendly and that they needed to up the tempo.
"I was very pleased with the way they responded to that. They are hurt after losing at home, something they're not used to.
"But we'll pick them up on Monday when we start preparing for a very tough away game at Southampton."