كتب : Hatem Maher
Midfielder Stephane Darbion put Ajaccio ahead on the hour mark when he latched onto Abou-Mosallam's deft through pass to slot home.
The Egyptian winger made his second appearance for Ajaccio after recovering from a hamstring injury that sidelined him for four games.
Clermont's Bruno Grougi secured a share of spoils with a last-minute goal.
Ajaccio, who extended their winless streak to six games, lie fourth from bottom on 26 points, just two above the relegation zone.
Abou-Mosallam joined Ajaccio on a six-month loan from Strasbourg after failing to prove himself at the latter club.
He hopes to play on a regular basis in order to return to Egypt's squad.