What is the role of 方 in 貽笑大方？
the 國語辭典 listed: 貽笑大方 is derived from 見笑大方

http://dict.revised.moe.edu.tw/cgi-bin/cbdic/gsweb.cgi?o=dcbdic&amp;searchid=Z00000093396

then 見笑大方 is derived from 莊子﹒秋水

http://ctext.org/zhuangzi/floods-of-autumn/zh


  吾長見笑於大方之家


it's a comment made by 河伯 (uncle river), when he reached the sea.

again, the 國語辭典 explained "大方之家" as "懂得大道理的人" (~ experts)

http://dict.revised.moe.edu.tw/cgi-bin/cbdic/gsweb.cgi?o=dcbdic&amp;searchid=Z00000040658

and "大方" as "有名的大家"

http://dict.revised.moe.edu.tw/cgi-bin/cbdic/gsweb.cgi?o=dcbdic&amp;searchid=Z00000040654

"方" is not a classifier in this usage. as i "google", some remarks of "方" in literatures of yore were "道" (tao, the proper way).