Meanwhile, 18-year-old defender Sam Hutchinson has signed a new four-year contract at Stamford Bridge, following Scott Sinclair's commitment to a long-term deal last week.
After a dispute over payment with the Turkish club Riza failed to hold down permanent deals at Shrewsbury and Aldershot and now finds himself on non-contract terms at Bridge Road.
Clarke had two years left of his current deal at Stamford Bridge after signing a new contract in the wake of Jose Mourinho's departure as manager in September 2007.
She raised the issue after it was announced that Forth Crossing Bridge Constructors, the consortium responsible for delivering the principal contract for the crossing, had struck deals with "major international steel suppliers in China and the EU".