Devotees of EU can die horribly (8)
I believe the answer is:
audience
'devotees of' is the definition.
The definition suggests a singular noun which matches the answer.
'eu can die horribly' is the wordplay.
'horribly' indicates anagramming the letters (a horribly wrong version of the letters).
'eu'+'can'+'die'='eucandie'
'eucandie' with letters rearranged gives 'AUDIENCE'.
Can you help me to learn more?
(Other definitions for audience that I've seen before include "Formal interview with very important person" , "They observe" , "The group listens or watches" , "Assembly gathered to watch, say, a play" , "Formal meeting with the Pope" .)