Anyone can edit this when it’s keyed in at the start (4)
I believe the answer is:
wiki
'anyone can edit this' is the definition.
(website anyone can edit eg Wikipedia)
'when it's keyed in at the start' is the wordplay.
'at the start' suggests taking the first letters.
The initial letters of 'when its keyed in' is 'WIKI'.
(Other definitions for wiki that I've seen before include "means to collaborate on a website" , "result of online co-operation" .)