Officer back in the corps (3)
I believe the answer is:
pro
'officer' is the definition.
The answer and definition can be both people as well as being singular nouns.
Perhaps you can see a link between them that I can't see?
'back in the corps' is the wordplay.
'back' shows that the letters should be reversed in order.
'in' indicates a hidden word.
'orp' can be found hidden inside 'corps'.
'orp' in reverse letter order is 'PRO'.
Can you help me to learn more?
(Other definitions for pro that I've seen before include "Prefix meaning for" , "gets paid to play?" , "Professional; advantage" , "With qualifications" , "Golfer" .)