They break the law and stow away in ships (8)
I believe the answer is:
brigands
'they' is the definition.
Both the definition and answer are plural nouns.
Perhaps there's a link between them I don't understand?
I cannot understand how the remainder of the clue works.
Can you help me to learn more?
(Other definitions for brigands that I've seen before include "Pirates on land" , "Bandits" , "Armed thieves" , "Highway robbers" .)