Frank, the first original writer (4)
I believe the answer is:
open
'frank' is the definition.
(synonyms)
'the first original writer' is the wordplay.
'the first original' becomes 'o' (1st letter of 'original').
'writer' becomes 'pen' (something which writes).
'o'+'pen'='OPEN'
(Other definitions for open that I've seen before include "Unrestricted; ready for business" , "Overt" , "Not closed or obstructed" , "Frank - ready for business" , "Public" .)