What a sailor could do with a pin (5)
I believe the answer is:
belay
This could be a double definition.
'what a sailor could do' is the first definition.
The definition suggests a singular noun which matches the answer.
'pin' is the second definition.
The answer and definition can be both to do with contact as well as being verbs in their base form.
Perhaps they are linked in a way I don't understand?
'with a' is the link.
Can you help me to learn more?
(Other definitions for belay that I've seen before include "Make fast" , "Turn a rope round something to secure it" , "Stop" .)