Smithies, who is reportedly attracting interest from Tottenham, QPR and Everton, has been offered a new contract by Clark this week having turned down a previous deal.
Clark said: "He's an outstanding young footballer, an outstanding man and a terrific lad and we are trying our very best to keep him at Huddersfield Town, but the vultures are swarming.
"We've got to try and convince him he is best off with us, he will eventually go right to the top and hopefully with Huddersfield.
"We want him to be part of what we are trying to build. We have talked with him in the last week and have put another contract on the table for him to consider and to convince him that he is better off here at this stage in his career."