Old writer is generally accessible (4)
I believe the answer is:
open
'generally accessible' is the definition.
'open' can be an answer for 'accessible' (something open can be accessed). I am not certain of the 'generally' bit.
'old writer' is the wordplay.
'old' becomes 'o' (common abbreviation eg in OE for Old English).
'writer' becomes 'pen' (something which writes).
'o'+'pen'='OPEN'
'is' acts as a link.
Can you help me to learn more?
(Other definitions for open that I've seen before include "still in debate" , "Overt" , "Contest that includes all comers" , "Not yet decided - to start" , "Public" .)