#1 on BBC's list of greatest 21st-century TV series

THEWIRE

["This gritty Baltimore drama redefined television storytelling with its realistic portrayal of urban life."]

This clue refers to "The Wire," a critically acclaimed TV series that topped the BBC's list of the greatest 21st-century shows. The answer is written as "THEWIRE" without spaces, which is common in crossword puzzles for multi-word titles. If you're familiar with the show or the BBC's ranking, this should be straightforward.