Hairstyle worn by sailor and his colleague (5)

I believe the answer is:
bosun
'his colleague' is the definition.
The answer is a person as well as being a singular noun. This is suggested by the definition.
'hairstyle worn by sailor' is the wordplay.
'hairstyle' becomes 'bun'.
'worn by' indicates putting letters inside (outside letters are worn by those on the inside).
'sailor' becomes 'os' (ordinary seaman).
'bun' placed around 'os' is 'BOSUN'.
'and' acts as a link.
Can you help me to learn more?
(Other definitions for bosun that I've seen before include "A diminutive boatswain" , "Ship's officer in charge of equipment and crew" , "Officer on board" , "chair for some work on the side" , "A short boatswain" .)
