How many letters does the top answer for “make a sound like a clock or a timer” have?

The most common answer is ticktack (8 letters).

Crossword clue: make a sound like a clock or a timer

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

ticktack 8 letters wn-def

system of signalling by hand signs used by bookmakers at racetracks

ticktock 8 letters wn-def

steady recurrent ticking sound as made by a clock

make a cat-like sound 50% similar → miaou, miaow