The Republic of Ireland international missed the 2-0 defeat to Tottenham last weekend with a sickness bug.
But Clark resumed training earlier this week and is in contention for the showdown against Roberto Martinez's team at Villa Park.
Midfielder Gardner is still struggling with a back problem, while winger Marc Albrighton has undergone a minor throat operation.
"Ciaran is fine," said manager Paul Lambert. "He has trained this week and everybody else is pretty good."