Nothing by the writer is widely known (4)
I believe the answer is:
open
'widely known' is the definition.
(I've seen this before)
'nothing by the writer' is the wordplay.
'nothing' becomes 'o' (O resembles 0).
'by' says to put letters next to each other.
'the writer' becomes 'pen' (something which writes).
'o'+'pen'='OPEN'
'is' is the link.
(Other definitions for open that I've seen before include "Frank - accessible" , "Frank and unlocked" , "Candid; ajar" , "Ready for business; spread out; manifest" , "Allowing access" .)