Head of army, for example, is giving protection (5)
I believe the answer is:
Here is my best explanation:
'protection' is the definition.
(aegis is a kind of protection)
'head of army for example is' is the subsidiary indication.
'head of' says to take the initial letters.
'for example' becomes 'eg' ('e.g.' can be a synonym of 'for example').
The first letter of 'army' is 'a'.
'giving' is the link.
(Other definitions for aegis that I've seen before include "Patronage", "Protection - guardianship", "Protection - patronage", "Sponsorship", "Protection (originally of Zeus)", "Protection or support", "Backing or support", "Protection (originally a shield)", "Protection or sponsorship" and "Kindly protection".)