(right) up (one's) alley definition
right up one's alley
Also, right down one's alley. In one's specialty, to one's taste, as in Writing press releases is right up her alley, or He loved opera, so this program of arias was right down his alley. These idioms use alley in the sense of "one's own province," a usage dating from the early 1600s. [First half of 1900s] Also see cup of tea.