Sailor's rank (6)
I believe the answer is:
rating
I believe this clue is a double definition.
'sailor's' is the first definition.
(British term for a naval enlisted man)
'rank' is the second definition.
(rating is a kind of rank)
(Other definitions for rating that I've seen before include "Grading or ranking" , "Angry reprimand for non-commissioned sailor?" , "Non-commissioned sailor in the Royal Navy" , "Grade or assessment" , "Classification or NCO sailor" .)