In grief, a cadet at the front (6)
I believe the answer is:
facade
'the front' is the definition.
(facade is a kind of front)
'in grief a cadet' is the wordplay.
'in' indicates a hidden word.
'FACADE' can be found hidden inside 'grief a cadet'.
'at' is the link.
(Other definitions for facade that I've seen before include "External surface" , "Series of notes" , "exterior" , "Front of building or outer appearance" , "Front presented" .)