How many letters does the top answer for “causing to move repeatedly from side to side” have?

The most common answer is shake (5 letters).

Crossword clue: causing to move repeatedly from side to side

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

shake 5 letters wn-def

move or cause to move back and forth

waggle 6 letters wn-def

move from side to side

move from side to side 50% similar → wag, waggle