Look into smash in mountain event (6)
I believe the answer is:
slalom
'event' is the definition.
(slalom is a kind of event)
'look into smash in mountain' is the wordplay.
'look' becomes 'lo' (archaic exclamation meaning 'look!').
'into' is an insertion indicator.
'smash in mountain' becomes 'slam' (I am not sure about this - if you are sure you should give a lot more credence to this answer).
'lo' placed within 'slam' is 'SLALOM'.
Can you help me to learn more?
(Other definitions for slalom that I've seen before include "Ski race down zig-zag course" , "Winding ski-run" , "Windy skiing event" , "Downhill skiing race" , "Downhill ski event" .)