Protection
'protection' is the definition.
(I know that defence is a type of protection)
This is the entire clue.
(Other definitions for defence that I've seen before include "See 12" , "The D in MoD" , "team of lawyers" , "Resistance to attack" , "A means of protecting from attack" .)
'protection' is the definition.
(aegis can mean someone's guidance or protection)
This is the entire clue.
(Other definitions for aegis that I've seen before include "Protection or support" , "Protection, backing" , "Custody" , "Protection or sponsorship" , "Friendly endorsement and guidance" .)