Old writer in annual golf event (4)
I believe the answer is:
open
'annual golf event' is the definition.
(the British Open)
'old writer' is the wordplay.
'old' becomes 'o' (common abbreviation eg in OE for Old English).
'writer' becomes 'pen' (I've seen this before).
'o'+'pen'='OPEN'
'in' is the link.
(Other definitions for open that I've seen before include "Candid or unlocked" , "Not shut or secret" , "Unlock" , "Allowing entry and exit" , "William --, English poet" .)