Horrible pirate provided opening shot (8)
I believe the answer is:
aperitif
'opening shot' is the definition.
(alcohol drunk at the start of a meal)
'horrible pirate provided' is the wordplay.
'horrible' indicates an anagram.
'provided' becomes 'if' (eg 'provided it's sunny' means 'if it's sunny').
'pirate' with letters rearranged gives 'aperit'.
'aperit'+'if'='APERITIF'
(Other definitions for aperitif that I've seen before include "Alcoholic drink before a meal, like sherry" , "Pre-nosh tipple?" , "it leads to blow-out" , "Alcoholic drink to stimulate appetite" , "it's served before dinner" .)