Behaved like a trained cadet (5)
I believe the answer is:
acted
'behaved' is the definition.
('act' can be a synonym of 'behave')
'trained cadet' is the wordplay.
'trained' indicates anagramming the letters (to train can mean to grow something into a shape).
'cadet' with letters rearranged gives 'ACTED'.
'like a' is the link.
(Other definitions for acted that I've seen before include "did something!" , "produced an effect" , "Cadet (anag)" , "Behaved or performed" , "took part in simulation" .)