Drink with a Caledonian companion (6)
I believe the answer is:
scotch
'drink' is the definition.
(Scotch is an example)
'with a caledonian companion' is the wordplay.
'with' says to put letters next to each other.
'a caledonian' becomes 'Scot' (Caledonia was the Latin name for Scotland).
'companion' becomes 'ch' (Companion of Honour).
'scot'+'ch' is 'SCOTCH'.
(Other definitions for scotch that I've seen before include "Kill in Caledonia?" , "A short" , "See 1" , "Put a stop to - whisky" , "Cut - wedge - whisky" .)