Sister nurses veteran MOD employee (7)
I believe the answer is:
soldier
'mod employee' is the definition.
'sister nurses veteran' is the wordplay.
'sister' becomes 'sr' (I've seen this in other clues).
'nurses' is an insertion indicator.
'veteran' becomes 'oldie' (I've seen this before).
'sr' enclosing 'oldie' is 'SOLDIER'.
(Other definitions for soldier that I've seen before include "piece of bread" , "Member of the armed forces" , "part of breakfast perhaps" , "mercenary?" , "Server in army" .)