Horrible tales by eccentric (7)
I believe the answer is:
beastly
'horrible' is the definition.
(thesaurus)
'tales by eccentric' is the wordplay.
'eccentric' is an anagram indicator.
'tales'+'by'='talesby'
'talesby' with letters rearranged gives 'BEASTLY'.
(Other definitions for beastly that I've seen before include "Bestial" , "Brutish" , "Horrid" , "Brutal - foul" , "Very unpleasant" .)