Porter maybe carrying small drink up mountain (6)
I believe the answer is:
alpine
'mountain' is the definition.
(I've seen this before)
'porter maybe carrying small drink up' is the wordplay.
'porter maybe' becomes 'ale' (type of alcoholic drink).
'carrying' is an insertion indicator.
'small drink' becomes 'nip' (I've seen this before).
'up' says the letters should be written in reverse (in down clue: letters go upwards).
'nip' written backwards gives 'pin'.
'ale' going around 'pin' is 'ALPINE'.
(Other definitions for alpine that I've seen before include "Plant of high mountains" , "from Germany, Austria etc" , "Relating to high mountains" , "Relating to a European mountain range" , "To do with great European mountains" .)