An arresting thing for a sailor to say? (5)
I believe the answer is:
belay
'say?' is the definition.
Although both the answer and definition are singular nouns, I don't understand how they can define each other.
I cannot understand how the rest of the clue works.
Can you help me to learn more?
(Other definitions for belay that I've seen before include "Turn a rope round something to secure it" , "Make fast" , "Stop" .)