Non-professional guards not just about serving protocol (10)
I believe the answer is:
ceremonial
'serving protocol' is the definition.
'non-professional guards not just about' is the wordplay.
I cannot quite understand how this works, but
'about' could be 're' (regarding) and 're' is found within the answer.
This explanation may well be incorrect...
(Other definitions for ceremonial that I've seen before include "Official" , "Ritual(istic)" , "Ritual procedure" , "Purely formal" .)