I would play 3421 if all fit and willing. Clarke is a back 4 man which means finding a right back from somewhere. But i would go with-
Marshall
Mckenna. Mulgrew. Tierney
Fraser. Mcginn Mctominay Robbo
Forrest. Christie
Griffiths
Subs: Snodgrass, Mclean, Paterson, Mcburnie, Taylor, Souttar, Mclaughlin, Gilmour, Jack, Burke, Armstrong, Mcgregor, Fleck