Drink for clergyman upset by opening (8)
I believe the answer is:
vermouth
'drink' is the definition.
(vermouth is a kind of drink)
'clergyman upset by opening' is the wordplay.
'clergyman' becomes 'rev' (short for reverend).
'upset' says the letters should be written in reverse.
'by' is a charade indicator (letters next to each other).
'opening' becomes 'mouth' (mouth is a kind of opening).
'rev' back-to-front is 'ver'.
'ver'+'mouth'='VERMOUTH'
'for' is the link.
(Other definitions for vermouth that I've seen before include "Herb-flavoured wine drunk with gin" , "Drink" , "Flavoured wine often mixed with gin" , "Wine flavoured with aromatic herbs" , "It, possibly" .)