A mark for every run (7)
I believe the answer is:
scarper
'run' is the definition.
('scarper' can be a synonym of 'run')
'a mark for every' is the wordplay.
'a mark' becomes 'scar' (I've seen this before).
'for every' becomes 'per' (I've seen this before).
'scar'+'per'='SCARPER'
(Other definitions for scarper that I've seen before include "Clear off!" , "Damage" , "Run away (colloq.)" , "Take to one's heels, cut and run" , "Vamoose" .)