Witness has set brandy cocktail (9)
I believe the answer is:
bystander
'witness' is the definition.
(I know that bystander is a type of witness)
'set brandy cocktail' is the wordplay.
'cocktail' indicates anagramming the letters.
'set'+'brandy'='setbrandy'
'setbrandy' with letters rearranged gives 'BYSTANDER'.
'has' acts as a link.
(Other definitions for bystander that I've seen before include "Non-participant spectator" , "Watcher of occurrence" , "Non-partcipating spectator" , "Onlooker (often innocent)" , "Bad sentry may be an onlooker" .)