The Chelsea forward headed home a cross from left-back Goran Popov with eight minutes remaining, marking his sixth goal of the season.
Clarke said: "Romelu has done well, he is a big talent, he has got a big future ahead of him in the game.
"The fact he couldn't get in the team for most of the season is down to the form of Shane Long who shouldn't be forgotten today.
"Shane made a difference when he came onto the pitch, he tied up the other centre-back, has given a bit more space to Romelu, and maybe that's why he has got the space for the winning goal.
"It's a team effort and we don't like to single out individuals."
But the Baggies boss was non-committal when asked whether Chelsea will recall Lukaku in January.
Clarke said: "He is on a season-long loan but there is an opportunity for the parent club to take him back in January.
"I can't affect it so I don't like to talk about it."
Clarke felt Albion were below their best in securing their first win in five games.
He said: "It was another performance where we were a bit scratchy. We are not quite flowing as we were early in the season.
"When you are coming in after four games without a win, there comes a bit more pressure on it.
"We spoke about it before the game. It was a big game for us today and it was important we got the three points."