Terribly feral Dutch king (6)
I believe the answer is:
alfred
'king' is the definition.
(I've seen this before)
'terribly feral dutch' is the wordplay.
'terribly' is an anagram indicator.
'dutch' becomes 'd' (common abbreviation).
'feral' anagrammed gives 'alfre'.
'alfre'+'d'='ALFRED'
(Other definitions for alfred that I've seen before include "Great English king" , "Saxon king" , "Royal one across burner" , "- - Hitchcock" , "King after Ethelred" .)