The 19-year-old, who has scored twice for the Baggies, was unavailable for international duty with Belgium because of pain in his right ankle but Clarke is confident the problem is only minor.
He told the official club website: "We're hopeful Lukaku will be fit. He's had a pain in his ankle for a few weeks. He felt it again when he came off the bench against QPR and didn't feel it was right to go (on international duty).
"He went across and got it assessed by the Belgium doctor and got sent back. It's not a big problem but it's one we're mindful we don't want to become a big problem. We're monitoring it."
Winger Jerome Thomas, meanwhile, is continuing his return to full fitness after a minor knee operation, and Clarke added: "Jerome trained last week and is on the way back."