Adult enthralled by scariest turbulent flight (9)
I believe the answer is:
staircase
'flight' is the definition.
(a flight of stairs)
'adult enthralled by scariest turbulent' is the wordplay.
'adult' becomes 'a' (abbreviation).
'enthralled by' indicates putting letters inside ('enthral' can mean 'capture').
'turbulent' is an anagram indicator.
'scariest' is an anagram of 'stircase'.
'a' put into 'stircase' is 'STAIRCASE'.
(Other definitions for staircase that I've seen before include "It's Caesar (anag.)" , "Group of joined locks on a canal" , "Means of moving from one floor to another" , "Set of steps" , "Route between floors" .)