How many letters does the top answer for “carefully observant or attentive; on the lookout for possible danger” have?

The most common answer is vigilant (8 letters).

Crossword clue: carefully observant or attentive; on the lookout for possible danger

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

vigilant 8 letters wn-def

carefully observant or attentive; on the lookout for possible danger

wakeful 7 letters wn-def

carefully observant or attentive; on the lookout for possible danger