Crossword clue: a three-masted vessel, having her foremast and mainmast squarerigged, and her mizzenmast schooner-rigged.

The most common answer is bark (4 letters).

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

Possible answers

bark 4 letters web-def

tough protective covering of the woody stems and roots of trees and other woody plants

barque 6 letters web-def

a sailing ship with 3 (or more) masts