Runner seen in Lusk Island (3)
I believe the answer is:
ski
'runner' is the definition.
(something which 'runs', ie moves quickly on snow)
'in lusk island' is the wordplay.
'in' says the answer is hidden in the clue.
'SKI' is hidden within 'lusk island'.
'seen' is the link.
(Other definitions for ski that I've seen before include "Winter sport equipment" , "Aid to movement on snow" , "Take part in a winter sport" , "Glide on snow with special footwear" , "What one might do in Alps" .)