Number 8 Leamy has been ruled out of action for at least five weeks with the knee injury he sustained in the game against the Scarlets last Friday.
Munster will be aiming to continue their impressive start to their European title defence with a third straight win, or at least come away with a losing bonus point as they did last season.
This term, Tony McGahan's men have already triumphed over newcomers Montauban and secured a crucial away win at Sale Sharks in round 2.
Clermont Auvergne currently lie in third position in Pool 1, having been beaten by Sale at home before bouncing back with a 24-19 win over Montauban last time out.
Looking forward to the game, Munster team manager Shaun Payne said: "Traditionally in the pool stages of the Heineken Cup we played the strongest team in the pool first and last. It always seemed to pan out like that.
"To play a strong team like Clermont Auvergne in the back-to-back games is a new situation for us.
"If we could go over there and scratch out a result, it would be massive for us. There will be pressure on them.
"We are away from home against an excellent team. We tend to play at our best when we are under that kind of pressure."
MUNSTER Squad (v Clermont Auvergne): Backs (11) - Tomas O'Leary, Peter Stringer, Ronan O'Gara, Paul Warwick, Lifeimi Mafi, Keith Earls, Barry Murphy, Kieran Lewis, Ian Dowling, Doug Howlett, Anthony Horgan.
Forwards (15) - Marcus Horan, Federico Pucciariello, John Hayes, Tony Buckley, Denis Fogarty, Frankie Sheahan, Mick O'Driscoll, Paul O'Connell (capt), Donncha O'Callaghan, Donnacha Ryan, Alan Quinlan, David Wallace, James Coughlan, Niall Ronan, John O'Sullivan.