How many letters does the top answer for “the act of physically reaching or thrusting out” have?

The most common answer is reach (5 letters).

Crossword clue: the act of physically reaching or thrusting out

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

reach 5 letters wn-def

reach a destination, either real or abstract

stretch 7 letters wn-def

occupy a large, elongated area

the act of reaching out 60% similar → outreach