Ditch joint set-up (8)
I believe the answer is:
jettison
'ditch' is the definition.
(to jettison is to ditch or discard)
'joint set-up' is the wordplay.
'up' indicates anagramming the letters (letters get chucked up).
'joint'+'set'='jointset'
'jointset' with letters rearranged gives 'JETTISON'.
(Other definitions for jettison that I've seen before include "Abandon or throw overboard" , "Deliberately dump overboard" , "Chuck overboard" , "Eject" , "Form of motor racing" .)