A 45-year-old man was fatally shot during a clash on an MTA train rumbling through the Bronx early Friday — just a mile from where one man was killed and five people were wounded in another train shooting last week, police said. The downtown D train was rumbling toward the 182-183rd Sts. station at Grand Concourse in Fordham just after 5 a.m. when an argument broke out, cops said. During the ...