Protection from extremely aggressive soldiers (5)
I believe the answer is:
aegis
'protection' is the definition.
(aegis can mean someone's guidance or protection)
'extremely aggressive soldiers' is the wordplay.
'extremely' means to remove the middle letters (only the extremes of the word are used).
'soldiers' becomes 'GIs' (GI is an informal term for a US soldier).
'aggressive' with its centre removed is 'ae'.
'ae'+'gis'='AEGIS'
'from' acts as a link.
(Other definitions for aegis that I've seen before include "Protection - patronage" , "shelter" , "Protection (originally a shield)" , "Protection (of someone)" , "Backing or support" .)