Arranging a scariest flight (9)
I believe the answer is:
staircase
'flight' is the definition.
(a flight of stairs)
'arranging a scariest' is the wordplay.
'arranging' indicates an anagram.
'a'+'scariest'='ascariest'
'ascariest' with letters rearranged gives 'STAIRCASE'.
(Other definitions for staircase that I've seen before include "Means of moving from one floor to another" , "Set of steps" , "Route between floors" , "Indoor flight" , "part of the mansion?" .)