Are you meaning tagname from attributdefinition you would like sort. Do you want rebuild a block with attributes.
Another way without lisp is, you take a copy of block, explode them and than use command attredef and you can by clicking on attdef byself choice direction which attdef should be sort.
It΄s a bit difficult to do that with lisp, you need a function which sort all tagnames from attdef and than you have to entmod them. I΄m not sure if it΄s the best way.