Evaluating a sailor (6)
I believe the answer is:
rating
I believe this clue is a double definition.
'evaluating' is the first definition.
(rating is a kind of evaluating)
'a sailor' is the second definition.
(British term for a naval enlisted man)
(Other definitions for rating that I've seen before include "Position on a scale" , "Valuation" , "Sailor - assessment" , "Angry reprimand for non-commissioned sailor?" , "Grading or ranking" .)