Dear Mohammad,  
  
The GT is not at all about market clearing and failures to clear (that's the  
New Keynesian version of Keynes's theory, which is misinterpreting the  
latter just as the writers of the so-called neoclassical synthesis did). I  
suggest that you read Keynes's 1933 papers on a monetary theory of  
production CWJMK, vol. XIII, pp. 408-411, and  XXIX, pp. 76-106.  
  
With best wishes,  
  
Claude Gnos