Soldier in theatre of war once briefly sent back (3)
I believe the answer is:
man
'soldier' is the definition.
(man can mean a soldier)
I don't understand how the remainder of the clue works.
Can you help me to learn more?
(Other definitions for man that I've seen before include "Staff the island" , "Isle of ..., ... o'war" , "just one" , "us?" , "Irish Sea isle" .)