Mountain air? (5)
I believe the answer is:
yodel
'mountain air?' is the definition.
(I've seen this before)
This is all the clue.
(Other definitions for yodel that I've seen before include "make an off-peak call" , "Sing (in the Alps)" , "Sing like the Lonely Goatherd?" , "Sing in Tyrolean fashion" , "Sing (Swiss style)" .)