Runs, leaving footmarks on the snow (7)
I believe the answer is:
sprints
'runs' is the definition.
(sprinting is a kind of running)
'footmarks on the snow' is the wordplay.
'footmarks' becomes 'prints' ('print' can be a synonym of 'footmark').
'on' means one lot of letters go next to another.
'the snow' becomes 's' (this could be a standard abbreviation which I don't know about).
'prints' after 's' is 'SPRINTS'.
'leaving' is the link.
Can you help me to learn more?
(Other definitions for sprints that I've seen before include "Darts" , "Dashes" , "careers" .)