New cadet took part (5)
I believe the answer is:
acted
'took part' is the definition.
(as in an actor taking a part in a production)
'new cadet' is the wordplay.
'new' indicates an anagram.
'cadet' with letters rearranged gives 'ACTED'.
(Other definitions for acted that I've seen before include "Cadet (anag)" , "Performed (in a play)" , "Performed on stage" , "produced an effect" , "Posed as" .)