Albion have now won just one of their last nine Premier League away games after Moussa Sissoko's thunderbolt sealed the victory for the hosts.
Chris Brunt had cancelled out Yoan Gouffran's first-half opener, but Clarke was not happy with the lack of creativity in his side.
"I thought first half we were too passive in the game," he told Sky Sports. "We didn't pass the ball as well as we do and we didn't create enough.
"We had one or two half chances as Newcastle did. The goal came out of nowhere because the game was drifting towards a goalless first half and then we conceded the goal.
"The second half was good. We played with more intensity, got ourselves back in the game and then a wonder strike denied us any points.
"I just feel that we were feeling a bit sorry for ourselves at times so we spoke about starting the second half on the front foot and getting bodies further forward and getting pressure in and around their defensive area and it started to pay dividends for us.
"Obviously, we got the equaliser and got on top in the game and then they scored against the run of play. We just couldn't create the second equaliser."