How many letters does the top answer for “make (senses) more keen” have?

The most common answer is subtilise (9 letters).

Crossword clue: make (senses) more keen

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

subtilise 9 letters wn-def

make (senses) more keen

subtilize 9 letters wn-def

make (senses) more keen

make keen or more acute 60% similar → whet