How many letters does the top answer for “director of beavis and butt-head” have?

The most common answer is judge (5 letters).

Crossword clue: director of beavis and butt-head

1 answer found in Letterora's clue database (Wikidata facts, Open Trivia DB, WordNet and Webster definitions — all licensed sources).

judge 5 letters wd-fact-v3

determine the result of (a competition)

composer of beavis and butt-head 60% similar → judge

butt with the head 50% similar → headbutt

director of head-on 50% similar → akin