Rum soul — perhaps, the brother of Remus (7)
I believe the answer is:
romulus
'brother of remus' is the definition.
(I've seen this before)
'rum soul perhaps' is the wordplay.
'perhaps' indicates anagramming the letters.
'rum'+'soul'='rumsoul'
'rumsoul' is an anagram of 'ROMULUS'.
'the' acts as a link.
(Other definitions for romulus that I've seen before include "Twin brother of Remus" , "Founder of the Eternal City" , "Fratricide" , "One of the legendary founders of Rome" , "One brother founding Rome" .)