They aren't all at sea! (7)
I believe the answer is:
sailors
'they' is the definition.
Both the answer and definition are plural nouns.
Maybe there's an association 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 sailors that I've seen before include "Members of a ship's crew" , "Seamen" , "Mariners" .)