Used by a non-commissioned officer (naval) (4)
I believe the answer is:
worn
'used' is the definition.
(I've seen this in another clue)
I can't explain the rest of the clue.
Can you help me to learn more?
(Other definitions for worn that I've seen before include "Sported on the body" , "Second-hand" , "Frayed" , "Looking tired and exhausted" , "Shabby" .)