How many letters does the top answer for “lacking the ability or skill to perform effectively; inadequate” have?

The most common answer is ineffective (11 letters).

Crossword clue: lacking the ability or skill to perform effectively; inadequate

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

ineffective 11 letters wn-def

lacking the ability or skill to perform effectively; inadequate

inefficient 11 letters wn-def

lacking the ability or skill to perform effectively; inadequate