I think he was trying to create common ground with Tom at that point. I consider "fat Clemenza" in the same vein as Sol telling Tom, "the Don...was slippin'." He was trying to create an impression with Tom that the Corleones (but not Tom) were weak and old fashioned, and that the future belonged to him--and to Tom, who he would consider a partner in the drugs business.
I don't think he wanted Tom as a partner any more than he wanted Sonny. What he wanted was to muscle his way into the Corleone family, break it up and pick up the pieces.
If he was trying to con Tom at that meeting I think he failed. As bad a wartime consigliere as Tom may have been, he wasn't THAT stupid.
