Drink provided by pirate at sea (8)
I believe the answer is:
aperitif
'drink' is the definition.
(aperitif is a kind of drink)
'provided by pirate at sea' is the wordplay.
'provided' becomes 'if'.
'by' is a charade indicator (letters next to each other).
'at sea' indicates anagramming the letters.
'pirate' with letters rearranged gives 'aperit'.
'if' after 'aperit' is 'APERITIF'.
(Other definitions for aperitif that I've seen before include "Pre-dinner drink" , "Alcoholic drink before a meal, like sherry" , "An alcoholic drink before dinner, an appetiser" , "Appetite stimulant drink" , "Alcoholic drink to stimulate appetite" .)