Military student from DC ate bananas (5)
I believe the answer is:
cadet
'military student' is the definition.
(I've seen this before)
'dc ate bananas' is the wordplay.
'bananas' indicates an anagram (informal term for mad).
'dc'+'ate'='dcate'
'dcate' with letters rearranged gives 'CADET'.
'from' acts as a link.
(Other definitions for cadet that I've seen before include "Younger member of family" , "Armed services trainee" , "A trainee army officer" , "Trainee -- acted (anag)" , "officer of the future" .)