Recruit acted strangely (5)
I believe the answer is:
cadet
'recruit' is the definition.
(I've seen this before)
'acted strangely' is the wordplay.
'strangely' is an anagram indicator.
'acted' is an anagram of 'CADET'.
(Other definitions for cadet that I've seen before include "Trainee cop" , "One taking instructions" , "who needs to be properly trained?" , "Younger son" , "One in training" .)