Short film showing runner (3)
I believe the answer is:
ski
'runner' is the definition.
(ski is a kind of runner)
'short film' is the wordplay.
'short' means to remove the last letter.
'film' becomes 'skin' (I've seen this in other clues).
'skin' with its final letter taken off is 'SKI'.
'showing' is the link.
(Other definitions for ski that I've seen before include "Snow-runner" , "Travel across snow" , "Walk on snow" , "Winter-sports item" , "Alpine runner" .)