Sculptor with initial cast showing ruler in Asgard (4)
I believe the answer is:
odin
'ruler in asgard' is the definition.
(ruler of the Norse gods)
'sculptor with initial cast' is the wordplay.
'sculptor' becomes 'rodin' (Auguste Rodin was a French sculptor).
'with initial cast' means to remove the first letter (the initial letter is cast away).
'rodin' with its initial letter removed is 'ODIN'.
'showing' acts as a link.
(Other definitions for odin that I've seen before include "The supreme Norse god and creator" , "Old Scandinavian" , "Norse god, husband of Frigg, father of Thor" , "Mythological Norse god of war" , "Supreme god of war in Norse mythology" .)