How many letters does the top answer for “sensing an odor by inhaling through the nose” have?

The most common answer is sniff (5 letters).

Crossword clue: sensing an odor by inhaling through the nose

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

sniff 5 letters wn-def

perceive by inhaling through the nose

snuff 5 letters wn-def

sensing an odor by inhaling through the nose

perceive by inhaling through the nose 50% similar → sniff