Son of Odin (6)
(Other definitions for balder that I've seen before include "with less growth on" , "Son of Odin - having less on top?" , "Less hairy on top" , "Norse god - having less hair" .)
'son of odin' is the definition.
(I've seen this in another clue)
This is the entire clue.
(Other definitions for thor that I've seen before include "Scandinavian thunder-god" , "Son of Odin and Freya" , "Comic superhero" , "Mythical figure" , "Scandinavian god of thunder and the weather" .)