The Scotland head coach revealed Hibs striker Kevin Nisbet picked up a knock in training and will be unavailable for selection, while Motherwell right-back Stephen O’Donnell has been unable to travel to Copenhagen for Covid-19 protocol related reasons.
It means the manager is facing a right-sided crisis with all three contenders for the starting wing-back role – O’Donnell, Rangers right-back Nathan Patterson and Celtic winger James Forrest – all unavailable.
Forrest joined fellow Celtic star Greg Taylor and former team-mate Stuart Armstrong in dropping out of the squad due to injury.
Patterson, meanwhile, was announced alongside Aston Villa star John McGinn as being forced to follow government guidelines related to the potential spread of the virus.
It means Scotland will travel for the fixture with the Euro 2020 semi-finalists as a squad of only 18 out of the 26 originally named, though Oostende defender Jack Hendry will join up with them in Denmark having had to do his own Covid protocols in travelling from Denmark.
Clarke said: "We have one or two issues again in terms of Kevin Nisbet picked up a knock in training so he is out for this game, he should be hopefully available for the weekend.
"I am also looking to bring another forward player into the squad after this game.
"And we have a little issue with Stephen O'Donnell getting access to Denmark which is a little bit of a curve ball, which has caught us out a little bit.'
"It is just the way it is, different countries have different rules.
"The medical staff have been trying to find ways round it but we haven't managed to solve that particular problem.
"I started with a squad of 26 and we will travel to Denmark with 18.
"Another issue is Jack Hendry, who played in Belgium at nine o'clock on Sunday night and rather than fly him back here for his Covid test at 9am on Monday, the UEFA deadline, we Covid tested him in Belgium, he is okay and he will go direct to Denmark and meet up with the squad there.''