Stewart, a well-travelled former striker with over 650 professional appearances and almost two-hundred goals to his name, joins the club as a replacement for the departing Andy Davies.
The 46-year-old, who alongside development coach Brian Dutton has made the permanent move to the West Midlands to link-up with Clarke, admitted that the newly-former backroom group have a huge task ahead of them, but are excited to get going.
Speaking via the club's official website, Marcus said; "It’s great to be here. I have had conversations with the manager since he has been at the club and he just asked me if I would like to join him.
"There is a big rebuilding job here but I was delighted when he asked me and I am excited to get going. I have been out of work for six months now so it is nice to be back involved with a manager that I trust.
"We have got a big job on our hands with a fair few players leaving and with us looking to bring new players in as well."