Ultimately wicked beer in valley (4)
I believe the answer is:
dale
'valley' is the definition.
(I know that valley can be written as dale)
'ultimately wicked beer' is the wordplay.
'ultimately' suggests the final letters.
'beer' becomes 'ale' (type of beer).
The last letter of 'wicked' is 'd'.
'd'+'ale'='DALE'
'in' is the link.
(Other definitions for dale that I've seen before include "Valley; Trollope's Bell and Lily" , "Valley; man's name" , "An English valley" , "depression" , "Valley, particularly in Northern England" .)