It is a second loan spell at Blues for the 21-year-old Manchester United youngster, following an all too brief stint earlier this year, when he was injured just 14 minutes into his league debut
against Derby County.
"I was so impressed with the couple of days training he had with us and the short time he had on the pitch against Derby,” said Clark.
"He looked like an accomplished ball-playing centre-half, but he was still aggressive and he needed to be. We’ve monitored his progress since he's been back at Manchester United. We think he will play a huge part for us and we're delighted to have him back."
Clark continued: "Although Aaron (Martin), Will (Packwood) and Paul Robinson have done well, I feel we have to tighten up defensively because we are conceding too many goals and we need greater strength in depth.
"We didn't have a defender on the bench on Tuesday and Paul is on 13 yellows, so we have to bear that in mind as well."
Unfortunately for Blues, England U21 international Thorpe will not be available for Saturday's home game against Bournemouth because of a bout of illness, but he will return to full training at Wast Hills on Monday.
"Tom has had a bout of tonsillitis," confirmed Clark. "After three days out he had his first day back in training with Manchester United yesterday. He won't be available for Saturday but he will be fine to join us on Monday and will then be available for the rest of the season."