T-ara won Best Music Video award at what music award show that is held in South Korea and organized by LOEN Entertainment? 
T-ara videography:  In 2011, T-ara won Best Music Video at the 3rd Melon Music Awards for their number-one single of the year, "Roly-Poly". Melon Music Awards: The Melon Music Awards is a major music awards show that is held annually in South Korea and organized by LOEN Entertainment through its online music store, "Melon".
The Melon Music Awards