Long has been the subject of speculation linking him with a move back to his former club Reading.
However, Clarke said: "There has been nothing regarding Shane. There have been no bids and he is not for sale. His future is with us 100%."
Clarke admitted that Albion have rejected a bid - believed to be from Blackburn - for another Republic of Ireland international forward in Simon Cox.
Cox has struggled to win a first team place at The Hawthorns in the face of competition from the likes of Long, Peter Odemwingie and Marc-Antoine Fortune.
He was left out of the squad for Saturday's friendly at Barnsley.
Clarke added: "A club has put a bid in for him. It wasn't accepted but Simon didn't feel he was quite right to play."