Rival to nice little Italian lake outside Roman capital (10)
I believe the answer is:
competitor
'rival' is the definition.
(synonyms)
'to nice little italian lake outside roman capital' is the wordplay.
I cannot really see how this works, but
'to' is found in the answer.
'italian' could be 'i' (abbreviation for Italian) and 'i' is found within the answer.
This may be the basis of clue (or it may be nonsense).
Can you help me to learn more?
(Other definitions for competitor that I've seen before include "rival trader?" , "Sporting contest entrant" .)