Capital letter finally lost by famous lover (4)
I believe the answer is:
rome
'capital' is the definition.
(capital of Italy)
'letter finally lost by famous lover' is the wordplay.
'letter' becomes 'em' (I've seen this in other clues).
'finally lost' means to remove the last letter.
'by' says to put letters next to each other.
'famous lover' becomes 'rom' (I can't explain this - if you can you should believe this answer much more).
'em' with its final letter taken off is 'e'.
'e' put after 'rom' is 'ROME'.
Can you help me to learn more?
(Other definitions for rome that I've seen before include "church" , "Seat of Italian empire" , "When here, do as the citizens do" , "Capital city" , "When there, do as the native do" .)