Drop mark? Managed to keep it (7)
I believe the answer is:
discard
'drop' is the definition.
(thesaurus)
'mark? managed to keep it' is the wordplay.
'mark?' becomes 'scar' ('scar' can be a synonym of 'mark').
'managed' becomes 'did' ('do' can mean 'manage' as in 'do without').
'to keep it' is an insertion indicator.
'scar' going within 'did' is 'DISCARD'.
(Other definitions for discard that I've seen before include "Reject" , "Jettison" , "Abandon" , "Shed" , "Throw away or cast off" .)