Report returned with old soldier (7)
I believe the answer is:
trooper
'soldier' is the definition.
(trooper is a kind of soldier)
'report returned with old' is the wordplay.
'returned' shows that the letters should be reversed in order.
'with' means one lot of letters goes inside another.
'old' becomes 'o' (common abbreviation eg in OE for Old English).
'report' in reverse letter order is 'troper'.
'troper' enclosing 'o' is 'TROOPER'.
(Other definitions for trooper that I've seen before include "Cavalry 21" , "Cavalryman" , "Private soldier" , "Cavalry soldier" , "He swears" .)