Brother of Romulus (5)
I believe the answer is:
remus
'brother of romulus' is the definition.
(I've seen this before)
This is the entire clue.
(Other definitions for remus that I've seen before include "US relative who did accounts" , "Early city planner" , "Brother to fifty two across" , "Brother of Romulus" , "J. C. Harris's storyteller Uncle" .)