To move lightly means a lot to a runner (4)
I believe the answer is:
skim
'to move lightly' is the definition.
I can't judge whether this definition defines the answer.
'a lot to a runner' is the wordplay.
'a lot' becomes 'm'.
'to a' is a charade indicator (letters next to each other) (I've seen this in other clues).
'runner' becomes 'ski' (something which 'runs', ie moves quickly on snow).
'm' after 'ski' is 'SKIM'.
'means' acts as a link.
Can you help me to learn more?
(Other definitions for skim that I've seen before include "Glide smoothly over" , "copy information illegally" , "Remove top (of milk)" , "avoid paying income tax" , "Brush over" .)