Popov faces a three-match ban as a result of the incident, which came early in the second half after he had exchanged angry words with Spurs defender Kyle Walker.
Clarke confirmed disciplinary action will be taken against the Macedonia international, adding that his dismissal played a large part in Albion's 1-0 defeat at The Hawthorns.
Steve Clarke: "The game changed with the sending-off. I'm absolutely disgusted with Goran's behaviour.
"One of the group has let the players down. It changed the whole complexion of the game.
"It's difficult enough in the Premier League playing against 11 players, especially when you're playing against Tottenham.
"There's no excuse for that. There's no place for it in life, never mind on a football pitch.
"I would like to think that at some stage he will apologise. As always there will be disciplinary procedures taken against the player but they'll remain in-house."
In 1998 Clarke joined Newcastle United as assistant manager to Ruud Gullit, his former boss at Chelsea. Clarke was caretaker manager following Gullit's resignation, taking charge of one match, a 5–1 defeat against Manchester United.
Source: Newcastle United Mad