One to keep order at sea, mum seconds calls to arrest a sailor (6-2-4)
I believe the answer is:
master-at-arms
'one to keep order at sea' is the definition.
I can't judge whether this defines the answer.
'mum seconds calls to arrest a sailor' is the wordplay.
I cannot really see how this works, but
'mum' could be 'ma' (synonyms) and 'ma' is found within the answer.
'seconds' could be 's' and 's' is found within the answer.
'a' is present in the answer.
'sailor' could be 'tar' (slang term for a sailor) and 'tar' is found in the answer.
'calls' could be 'terms' (terming is a kind of calling) and 'terms' is located in the leftover letters.
This accounts for all the letters.
This explanation may well be incorrect...
Can you help me to learn more?
(Other definitions for master-at-arms that I've seen before include "Ship's chief police officer" , "enforcer of naval discipline" , "Naval chief petty officer" , "Senior naval petty officer responsible for discipline" , "Chief Petty Officer in charge of discipline" .)