The 21-year-old, who had a loan spell at Portsmouth earlier this season, has been called up amid a growing injury crisis for the Irish.
He will arrive in time to meet up with the rest of the squad ahead of Wednesday morning's training session in Malahide.
Manager Giovanni Trapattoni has lost Sean St Ledger, Glenn Whelan, James McClean and Kevin Doyle since naming his squad, and was only able to include Richard Dunne on a stand-by list with the central defender still recovering from injury.
Ciaran Clark, David Meyler and Robbie Brady have already been added to the original party, and Under-21 international Clifford will now join them.
Trapattoni is considering playing three central midfielders in the clash with Group C leaders Germany at the Aviva Stadium in Dublin with Keith Andrews, James McCarthy, Keith Fahey and Meyler the main contenders.
However, Clifford's arrival, if nothing else, will help the manager's work on the training ground by increasing the numbers of players with whom he is able to work as he drills his side ahead of a tough test.
- David Meyler