Golf competition half-seen after work (4)
I believe the answer is:
open
'golf competition' is the definition.
(The Open is a golf tournament)
'half-seen after work' is the wordplay.
'half' indicates taking half.
'after' says to put letters next to each other.
'work' becomes 'op' (abbreviation for opus).
'seen' with half the letters taken is 'en'.
'en' after 'op' is 'OPEN'.
(Other definitions for open that I've seen before include "sporting competition" , "See 12" , "Ready for business; spread out; manifest" , "Admitting customers" , "begin to > crack" .)