Coast Guard Academy student (5)
I believe the answer is:
cadet
'coast guard academy student' is the definition.
(I've seen this in another clue)
This is all the clue.
(Other definitions for cadet that I've seen before include "Junior officer; younger brother" , "Police force trainee" , "not the heir" , "One in training" , "Younger son's branch of a family" .)