How many letters does the top answer for “to move slowly and heavily.” have?

The most common answer is lug (3 letters).

Crossword clue: to move slowly and heavily.

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

lug 3 letters web-def

carry with difficulty

draw slowly or heavily 50% similar → cart, hale, haul

move heavily or clumsily 50% similar → lumber

someone who moves slowly 50% similar → plodder, slowcoach, slowpoke