Somewhat horrendous finale (3)
I believe the answer is:
end
'finale' is the definition.
(I've seen this before)
'somewhat horrendous' is the wordplay.
'somewhat' says the answer is hidden in the clue.
'END' can be found hidden inside 'horrendous'.
(Other definitions for end that I've seen before include "Extremity" , "Desired outcome" , "Extreme" , "Butt" , "Finish; goal" .)