How many letters does the top answer for “imp. of slee, to slay. slew. chaucer.” have?

The most common answer is slough (6 letters).

Crossword clue: imp. of slee, to slay. slew. chaucer.

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

slough 6 letters web-def

any outer covering that can be shed or cast off (such as the cast-off skin of a snake)

slow 4 letters web-def

not moving quickly; taking a comparatively long time

imp. of slee,to slay. chaucer. 80% similar → slowh