Polar vehicle (4)
(Other definitions for iceboat that I've seen before include "Arctic vessel" , "Ship used to clear way in polar waters" , "Craft" , "One'll break through the pack" , "it cuts through arctic seas" .)
'polar vehicle' is the definition.
(I've seen this in another clue)
This is the entire clue.
(Other definitions for sled that I've seen before include "Goods vehicle" , "Winter transport" , "Snow transport" , "Toboggan (mainly US)" , "American toboggan" .)