Assistant losing son at the end of a day in Rome (4)
I believe the answer is:
aide
'assistant' is the definition.
(aide is a kind of assistant)
I cannot understand how the remainder of the clue works.
(Other definitions for aide that I've seen before include "Military officer acting as assistant" , "Adviser or assistant" , "someone in assistance" , "Political assistant" , "Personal assistant in the military" .)