Nick, incision (5)
I believe the answer is:
notch
I believe this clue is a double definition.
'nick' is the first definition.
(both can mean a small cut or impression)
'incision' is the second definition.
(synonyms)
(Other definitions for notch that I've seen before include "Incision on an edge" , "Snick" , "Nick - incision" , "small score?" , "Mark indented in wood etc" .)