** Shares of Step One Clothing slip as much as 12.8% to A$1.635, set for their worst day since early May, if losses hold

** The online retailer says its founder and chief executive officer sold down about 8.97% shares in the co; while its chief legal officer has sold around a 1.1% stake

** Adds sale was undertaken at A$1.70 per share via a fully underwritten block trade

** CEO to remain co's largest shareholder, having a 57.91% stake after the sell-down

** Shares hit their lowest levels since early Sept

** Including day's moves, stock has risen ~68.7% this year

(Reporting by Archishma Iyer)

((Archishma.Iyer@thomsonreuters.com;))