Reject Mark did without (7)
I believe the answer is:
discard
'reject' is the definition.
(I've seen this before)
'mark did without' is the wordplay.
'mark' becomes 'scar' (mark left by an injury).
'without' means one lot of letters goes inside another.
'scar' put into 'did' is 'DISCARD'.
(Other definitions for discard that I've seen before include "Throw away or cast off" , "Reject" , "Abandon" , "Get rid of" , "Jettison" .)