God of thunder (4)
I believe the answer is:
'god of thunder' is the definition.
(Norse god of thunder)
This is all the clue.
(Other definitions for thor that I've seen before include "Thunderous god" , "Thursday is named after this Scandinavian god" , "Norse god of thunder - a weekday is named after him" , "The Thunderer" , "One of the Norse gods" .)