Throw with force (4)
(Other definitions for cast that I've seen before include "Dramatis personae" , "Throw off; select (actor)" , "Character" , "Mould; actors in a play" , "Personnel in a play" .)
'throw with force' is the definition.
(I've seen this in another clue)
This is all the clue.
(Other definitions for heave that I've seen before include "Hoist" , "Drag" , "Big effort" , "Pull hard; (sea) swell" , "Express" .)