Military student acted out (5)
I believe the answer is:
cadet
'military student' is the definition.
(I've seen this before)
'acted out' is the wordplay.
'out' is an anagram indicator (out can mean wrong or inaccurate).
'acted' anagrammed gives 'CADET'.
(Other definitions for cadet that I've seen before include "Police or armed forces trainee" , "Police force trainee" , "not the heir" , "who needs to be properly trained?" , "Younger member of family" .)