Rampaging pirate provided opening shot (8)
I believe the answer is:
aperitif
'opening shot' is the definition.
(alcohol drunk at the start of a meal)
'rampaging pirate provided' is the wordplay.
'rampaging' indicates an anagram (I've seen this in other clues).
'provided' becomes 'if' (eg 'provided it's sunny' means 'if it's sunny').
'pirate' anagrammed gives 'aperit'.
'aperit'+'if'='APERITIF'
(Other definitions for aperitif that I've seen before include "Preprandial drink" , "Appetite stimulant drink" , "Alcoholic beverage as an appetiser" , "Alcoholic drink before a meal, like sherry" , "Alcoholic drink to whet the appetite" .)