Possible Clues:

• Resident of the largest Spanish-speaking nation
• Like some tangos
• Fish a fellow caught in European river, not hard
• Are in the West, presumably, to take in Grand National
• Horrible tangerine, one from S America
• A charge, popular with race ultimately, for covering Grand National
• Buenos Aires resident
• Marine fish named for its silver color
• Silvery toff I introduced to composer
• Unexpectedly entering with a South American