How many letters does the top answer for “a steep-walled semicircular basin in a mountain; may contain a lake” have?

The most common answer is cirque (6 letters).

Crossword clue: a steep-walled semicircular basin in a mountain; may contain a lake

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

cirque 6 letters wn-def

a steep-walled semicircular basin in a mountain; may contain a lake

corrie 6 letters wn-def

a steep-walled semicircular basin in a mountain; may contain a lake

cwm 3 letters wn-def

a steep-walled semicircular basin in a mountain; may contain a lake