Clifford replaces Saracens number eight Billy Vunipola after he picked up an injury to his right knee during Saracens’ win against Sale Sharks on Saturday.
The squad will convene in Oxford for the three-day camp.
The camp will provide a chance for the squad to continue their preparations for the upcoming end-of-year series that will see England play Argentina (11 November), Australia (18 November) and Samoa (25 November).
“This camp in Oxford is a really positive opportunity for the group to come back together and sharpen our focus and preparation ahead of our first match against Argentina,” said England head coach Eddie Jones.
England training squad (revised):
Forwards: Jack Clifford (Harlequins), Dan Cole (Leicester Tigers), Tom Curry (Sale Sharks), Tom Dunn (Bath Rugby), Charlie Ewels (Bath Rugby), Ellis Genge (Leicester Tigers), Jamie George (Saracens), Dylan Hartley (Northampton Saints), Nathan Hughes (Wasps), Nick Isiekwe (Saracens), Maro Itoje (Saracens), Joe Launchbury (Wasps), Courtney Lawes (Northampton Saints), Joe Marler (Harlequins), Chris Robshaw (Harlequins), Sam Underhill (Bath Rugby), Harry Williams (Exeter Chiefs), Mako Vunipola (Saracens)
Backs: Mike Brown (Harlequins), Danny Care (Harlequins), Elliot Daly (Wasps), Owen Farrell (Saracens), George Ford (Leicester Tigers), Piers Francis (Northampton Saints), Alex Lozowski (Saracens), Jonny May (Leicester Tigers), Jack Nowell (Exeter Chiefs), Henry Slade (Exeter Chiefs), Marcus Smith (Harlequins), Ben Te’o (Worcester Warriors), Anthony Watson (Bath Rugby), Marland Yarde (Harlequins), Ben Youngs (Leicester Tigers)