One in rough currents in windy and icy passage (6,3)
I believe the answer is:
cresta run
'windy and icy passage' is the definition.
I don't know anything about this answer so I can't judge whether it can be defined by this definition.
'one in rough currents' is the wordplay.
'one' becomes 'a' (a thing is one thing).
'in' means one lot of letters goes inside another.
'rough' indicates anagramming the letters (a rough or broken ordering of the letters).
'currents' is an anagram of 'crestrun'.
'a' inserted into 'crestrun' is 'CRESTA RUN'.
'in' acts as a link.
Can you help me to learn more?
(Other definitions for cresta run that I've seen before include "tobogganing slope" , "Swiss skeleton toboggan track" , "Frozen channel" .)