A young lover is more befuddled by love (5)
I believe the answer is:
Here is my best explanation:
'a young lover' is the definition.
'more befuddled by love' is the subsidiary indication.
'befuddled' is an anagram indicator.
'by' says to put letters next to each other.
'love' becomes 'o' (In tennis, 'love' means 'zero').
'more' is an anagram of 'rome'.
'is' is the link.
(Other definitions for romeo that I've seen before include "Famous lover", "Lover boy", "Don Juan", "Comms code for R", "24's lover", "He's on the lookout for it?", "Literary lover", "Amorous male", "Tragic Shakespeare hero" and "Shakespearean hero".)