Crossword puzzle clue "first word of many letters"

First word across in the first-ever crossword (1913) and the first of a dozen appearances of the word in this puzzle's grid, written word search-style (left, right, down, and diagonally) ... Can you f

Many protagonists, and a hint to the four letters that make up each starred answer's first word

Letters on many business letters

Radio station whose call letters include the first three letters of its Ohio city

How many letters are in the longest answers in this puzzle - or how many of these answers there are

Premier League manager Wenger (the club he manages has the same first five letters as his first name)