Horrible duke almost satisfied after study (8)
I believe the answer is:
dreadful
'horrible' is the definition.
(I've seen this before)
'duke almost satisfied after study' is the wordplay.
'duke' becomes 'd'.
'almost' means to remove the last letter (most of the word but not all of it).
'satisfied' becomes 'full'.
'after' says to put letters next to each other.
'study' becomes 'read' (synonyms).
'full' with its final letter taken away is 'ful'.
'ful' after 'read' is 'readful'.
'd'+'readful'='DREADFUL'
(Other definitions for dreadful that I've seen before include "Dire, alarming" , "Horrible, shocking" , "Shockingly bad" , "Terrible" , "Atrocious, awful" .)