Writer of life story about Romeo (4)
I believe the answer is:
biro
'writer' is the definition.
(type of pen, something which writes)
'life story about romeo' is the wordplay.
'life story' becomes 'bio' (short for biography).
'about' indicates putting letters inside.
'romeo' becomes 'r' (phonetic alphabet: alpha, bravo, charlie etc.).
'bio' going around 'r' is 'BIRO'.
'of' acts as a link.
(Other definitions for biro that I've seen before include "Pocket item" , "Writing implement" , "writer" , "Lazlo -, ballpoint pen inventor" , "Type of ballpoint pen" .)