Quash spirit of the Highlands? (6)
I believe the answer is:
scotch
This clue is a double definition.
'quash' is the first definition.
(I've seen this before)
'spirit of the highlands?' is the second definition.
(Scotch whisky, alcoholic spirit)
(Other definitions for scotch that I've seen before include "Put an end to - as Jock might?" , "Put an end to, say rumour" , "Put an end to - in Caledonia?" , "Thwart - sort of broth, mist or egg" , "Cut - wedge - whisky" .)