How many letters does the top answer for “an organelle containing enzymes responsible for producing energy” have?

The most common answer is chondriosome (12 letters).

Crossword clue: an organelle containing enzymes responsible for producing energy

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

chondriosome 12 letters wn-def

an organelle containing enzymes responsible for producing energy

mitochondrion 13 letters wn-def

an organelle containing enzymes responsible for producing energy