The Newcastle United midfielder has made six appearances for the club since joining on loan last month, but his initial spell ended earlier this week.
Clark told Sky Sports News: "We think Shane's a terrific little player and he's a great kid; we're delighted that we'll have him for the rest of the season.
"I think the deal has benefited us, Newcastle and Shane. He's brought quality, tenacity, speed and energy and he puts in quality deliveries. You've also got to remember just how young he is as well."
Ferguson scored his first senior goal in the 4-0 win over Crystal Palace last week.