How many letters does the top answer for “a tense of verbs used in describing action that is on-going” have?

The most common answer is imperfect (9 letters).

Crossword clue: a tense of verbs used in describing action that is on-going

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

imperfect 9 letters wn-def

not perfect; defective or inadequate