The Baggies have rejected a bid believed to be in the region of £5m from QPR for the defender.
However, Clarke did admit that there is a buy-out clause in Olsson's contract which could be activated by one of six clubs this summer.
Reports have suggested that Olsson is keen to be based in London for family reasons but Clarke said: "I can confirm a bid has been turned down and I don't encourage any more bids, because Jonas is not for sale.
"I have spoken to Jonas and he says he is loving the football here, he is enjoying the position we are in, and he is looking forward to the rest of the season.
"He will remain a West Brom player and we don't have to sell anyone. He is not for sale, so there is no figure which is reasonable.
"There is a clause in Jonas' contract which comes into play during the summer. There are six clubs that can invoke that."