Story says:
"On Memorial Day 1927, brawls erupted in New York led by sympathizers of the Italian fascist movement and the Ku Klux Klan. In the fascist brawl, which took place in the Bronx, two Italian men were killed by anti-fascists. In Queens, 1,000 white-robed Klansmen marched through the Jamaica neighborhood, eventually spurring an all-out brawl in which seven men were arrested.
One of those arrested was Fred Trump of 175-24 Devonshire Rd. in Jamaica.
The predication for the Klan to march, according to a flier passed around Jamaica beforehand, was that "Native-born Protestant Americans" were being "assaulted by Roman Catholic police of New York City." "Liberty and Democracy have been trampled upon," it continued, "when native-born Protestant Americans dare to organize to protect one flag, the American flag; one school, the public school; and one language, the English language."
It's not clear from the context what role Fred Trump played in the brawl. The news article simply notes that seven men were arrested in the "near-riot of the parade," all of whom were represented by the same lawyers. Update: A contemporaneous article from the Daily Star notes that Trump was detained "on a charge of refusing to disperse from a parade when ordered to do so."