Injured Clifford to miss England campaign
Clifford, a replacement loose forward during England's Grand Slam march earlier this year, suffered the injury during the Premiership defeat at Exeter last weekend and will not return to action until early December.
"It's very disappointing and unfortunate that Jack has sustained his ankle injury, which will keep him out for approximately 10 weeks," said Harlequins Director of Rugby John Kingston on Friday.
Clifford has been involved in all but one of England's nine Tests under coach Eddie Jones, but just one of those eight caps was in the starting XV, against Wales in May.
England have a vacancy in their first-choice back row after James Haskell's foot injury, ahead of the upcoming Twickenham Tests against South Africa, Fiji, Argentina and Australia.
Clifford was competing with Teimana Harrison for the openside flanker's berth in Haskell's absence, but his upcoming operation has put a brake on his immediate England future.
"Jack is a fierce competitor and I have no doubt he will work exceptionally hard to get himself back on the field as quickly as possible," Kingston said.