Thorne has been sidelined since damaging his cruciate ligament in January, but has recently been linked with loan moves to Derby County and Watford.
However, West Brom boss Clarke does not want to rush Thorne back into first-team football and has put a temporary switch for the youngster on hold.
"At the moment the important thing for George is to concentrate on his fitness," said Clarke in the Express & Star after Thorne was substituted in a game against Liverpool's Under 21s on Sunday.
"He's had a couple of Under-21s games that he hasn't been able to finish so he's still looking for a little bit of fitness to take forward for the rest of the season.
"If George gets to a stage of his fitness where he's able to handle a loan move, then it's something we'd consider. But for now it's better he stays here and works with the medical people, who know how he's recovering."
Experienced midfielder Zoltan Gera is also working his way back to fitness after a knee injury and he was also taken off against Liverpool.
Clarke added: "We're in a position with 'Zolly' where we don't take any risks.
"He felt something in the game. His hamstring tightened a little bit so the no-risk policy means we took him off.
"He doesn't seem too bad, which is good - and George is similar."