how 5volt can be obtained from a 6volt transformer without uusing regulator?

 

You want 5 volt AC from a 6 volt ac transformer right off the secondary?

 

how 5volt can be obtained from a 6volt transformer without uusing regulator?

Depends on your intended load. The load will bring your 6v down to 5 on the output of the transformer. 5v. sounds like a cmos application, for which I would definitely use a regulator anyway.