Terrible death regarded as very nasty (5)
I believe the answer is:
hated
'very nasty' is the definition.
I can't judge whether this definition defines the answer.
'terrible death' is the wordplay.
'terrible' is an anagram indicator.
'death' anagrammed gives 'HATED'.
'regarded as' is the link.
Can you help me to learn more?
(Other definitions for hated that I've seen before include "Abominated" , "Death (anag)" , "Loathed" , "Seriously disliked" , "Detested" .)