How many letters does the top answer for “the front bowling pin in the triangular arrangement of ten pins” have?

The most common answer is headpin (7 letters).

Crossword clue: the front bowling pin in the triangular arrangement of ten pins

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

headpin 7 letters wn-def

the front bowling pin in the triangular arrangement of ten pins

kingpin 7 letters wn-def

the front bowling pin in the triangular arrangement of ten pins