Nominally, she sheds a little light on a Roman road (5)
I believe the answer is:
livia
'nominally' is the definition.
I don't know anything about this answer so I can't tell whether it can be defined by this definition.
'she sheds a little light on a roman road' is the wordplay.
'she sheds' becomes 'i' (I am not sure about this - if you are sure you should give a lot more credence to this answer).
'a little' suggests taking the first letters.
'on' is a charade indicator (letters next to each other).
'a roman road' becomes 'via' (I've seen this in another clue).
The first letter of 'light' is 'l'.
'i' put after 'l' is 'li'.
'li'+'via'='LIVIA'
Can you help me to learn more?
(Other definitions for livia that I've seen before include "Anna ..... is the literary Liffey" , "James Joyce christened the Liffey 'Anna ....'" , "Wife of Caesar Augustus" .)