Military student half-dead, grabbed by lion? (5)
I believe the answer is:
'military student' is the definition.
(I've seen this before)
'half-dead grabbed by lion?' is the wordplay.
'half' means to take half the letters.
'grabbed by' is an insertion indicator (inserted letters are grabbed inside).
'lion?' becomes 'cat' (lions are big cats).
'dead' with half the letters taken is 'de'.
'de' put into 'cat' is 'CADET'.
(Other definitions for cadet that I've seen before include "Younger son" , "Officer in training" , "aspiring officer" , "Police force trainee" , "Officer-trainee" .)