The France international linked up with the Baggies over the summer, with Marseille allowing him to leave on an initial season-long agreement.
It has not taken the 28-year-old winger long to make his mark in England, with a star showing against Sunderland on Saturday seeing him score one and make two more in a 3-0 victory.
Clarke is delighted to have Amalfitano's creativity at his disposal and admits he will be in a position to buy the former Sedan and Lorient forward next summer if he continues to impress.
He said in the Birmingham Mail: "There is an option to buy.
"I said in August I needed some more forward players to increase options.
"It also creates more problems for the opposition - the more good attacking players you have, the more problems you are likely to cause them."
Clarke, who drafted in nine fresh faces over the summer, added on his new-look side: "It takes time if you sign players and try to change things around.
"One or two other teams in the league have made some changes - Norwich, ourselves, Sunderland.
"Sometimes it takes a little bit of time to pick up the rhythm and get moving.
"Saturday was a step in the right direction but nothing more than that. Now we prepare for our next games."