Begin without concealment (4)
I believe the answer is:
open
I believe this is a double definition.
'begin' is the first definition.
(both can mean to start)
'without concealment' is the second definition.
(I've seen this before)
(Other definitions for open that I've seen before include "Candid or unlocked" , "Ready for business; spread out; manifest" , "Frank; unfold" , "Willing" , "This championship includes both professional and amateur golfers" .)