A fundraiser was an event that raised money for a charitable organization.
In 2370, Quark brought Julian Bashir a beverage, ostensibly a medicinal brew from the Bajoran monks to thank him for his participation in a fundraiser for the Bajoran War Orphans Fund. In reality, it was an anesthetic, part of Quark's plot to fix the darts match in Miles O'Brien's favor. (DS9: "Rivals")
Fundraising on Deep Space 9's Promenade required a license; doing so without a license was a violation of station regulation fifteen twenty six, paragraph seven. In 2374, Odo detained Vedek Solis in a holding cell for less than an hour after the vedek attempted to raise money for Bajoran flood victims without a license, something which made Kira Nerys upset. (DS9: "Tears of the Prophets")