Mark to score! (5)
I believe the answer is:
notch
This clue is a double definition.
'mark' is the first definition.
(a notch is a mark or scratch on something)
'score' is the second definition.
(I've seen this in another clue)
'to' is the link.
(Other definitions for notch that I've seen before include "Indentation - step up" , "Dent" , "Carved incision" , "Make the cut" , "Small V-shaped cut or indentation" .)