Occasionally, cadet soldiers provide protection (5)
I believe the answer is:
aegis
'protection' is the definition.
(aegis can mean someone's guidance or protection)
'occasionally cadet soldiers' is the wordplay.
'occasionally' means one should take alternating letters.
'soldiers' becomes 'gis' (GI is an informal term for a US soldier).
The alternating letters of 'cadet' are 'ae'.
'ae'+'gis'='AEGIS'
'provide' acts as a link.
(Other definitions for aegis that I've seen before include "Protection (originally of Zeus)" , "Protection (of someone)" , "Friendly endorsement and guidance" , "Protection, backing" , "Advocacy" .)