Officer requires agents organised to protect queen (8)
I believe the answer is:
sergeant
'officer' is the definition.
(sergeant is a kind of officer)
'agents organised to protect queen' is the wordplay.
'organised' is an anagram indicator.
'to protect' is an insertion indicator.
'queen' becomes 'er' (abbreviation for Elizabeth Regina).
'agents' is an anagram of 'sgeant'.
'sgeant' enclosing 'er' is 'SERGEANT'.
'requires' is the link.
(Other definitions for sergeant that I've seen before include "CARRY ON FILM" , "NCO or police officer ..." , "Soldier and lover in Hardy novel" , "Estrange (anag)" , "Military or police officer" .)