Crossword clue: a peculiar transparent worm of the genus sagitta, living at the surface of the sea. see sagitta.
1 answer found in Letterora's clue database (Wikidata facts, Open Trivia DB, WordNet and Webster definitions — all licensed sources).
Possible answers
any worm of the Chaetognatha; transparent marine worm with horizontal lateral and caudal fins and a row of movable curve