Leeds have given permission for Clayton to feature, while 21-year-old Agard - signed on loan from Everton until the end of the season - has also received the green light to be involved.
Former Lincoln midfielder Lee Frecklington is expected to miss out again with his ankle problem, and luckless striker Dave Hibbert is a long-term absentee with a dislocated knee and is not expected to return until March.
Playmaker George Boyd remains a doubt after he turned an ankle in training last weekend and missed Monday's impressive 4-1 win over Walsall.
Midfielder Charlie Lee is also battling an ankle injury which kept him out of Bank Holiday action.
Posh boss Gary Johnson returns to south-west London where he was born, growing up living opposite Craven Cottage and supporting Fulham as a boy.
Source: PA
Source: PA