Extremely short opening for drink (8)
I believe the answer is:
vermouth
'drink' is the definition.
(vermouth is a kind of drink)
'extremely short opening' is the wordplay.
'extremely' becomes 'very' (I've seen this before).
'short' means to remove the last letter.
'opening' becomes 'mouth' (mouth is a kind of opening**).
'very' with its last letter taken away is 'ver'.
'ver'+'mouth'='VERMOUTH'
'for' is the link.
(Other definitions for vermouth that I've seen before include "Wine flavoured with aromatic herbs" , "Flavoured wine used in cocktails" , "It, possibly" , "Herb-flavoured wine drunk with gin" , "Drink" .)