Playwright or raving egghead (5)
I believe the answer is:
wilde
'playwright' is the definition.
(I know that Wilde is a playwright)
'raving egghead' is the wordplay.
'raving' becomes 'wild' (synonyms).
'egghead' becomes 'e' (head letter of 'egg').
'wild'+'e'='WILDE'
'or' is the link.
(Other definitions for wilde that I've seen before include "He wrote The Ballad of Reading Gaol" , "Irish wit and playwright" , "Author of The Picture of Dorian Gray" , "Oscar or Kim?" , "Oscar, great Irish writer" .)