Crossword clue: an omission or neglect to do something, esp. that which ought to have been done. cf. malfeasance.
1 answer found in Letterora's clue database (Wikidata facts, Open Trivia DB, WordNet and Webster definitions — all licensed sources).
Possible answers
a failure to act when under an obligation to do so; a refusal (without sufficient excuse) to do that which it is your le