Unexpectedly scariest, a way up (9)
I believe the answer is:
staircase
'way up' is the definition.
I can't tell whether this definition defines the answer.
'unexpectedly scariest a' is the wordplay.
'unexpectedly' is an anagram indicator.
'scariest'+'a'='scariesta'
'scariesta' with letters rearranged gives 'STAIRCASE'.
Can you help me to learn more?
(Other definitions for staircase that I've seen before include "Group of joined locks on a canal" , "part of the mansion?" , "Indoor flight" , "Means of moving from one floor to another" , "A group of linked canal locks" .)