Scandinavian god of thunder (4)
I believe the answer is:
thor
'scandinavian god of thunder' is the definition.
(I've seen this before)
This is the entire clue.
(Other definitions for thor that I've seen before include "Germanic thunder god; early US IRBM" , "Scandinavian thunder-god" , "The Thunderer" , "Norse god of thunder - a weekday is named after him" , "Scandinavian god of thunder and the weather" .)