A cloud of smoke is said to cause dismay (5)
I believe the answer is:
appal
'dismay' is the definition.
(I know that dismay can be written as appal)
I can't explain the rest of the clue.
Can you help me to learn more?
(Other definitions for appal that I've seen before include "Outrage" , "expressed dismay" , "Cause to be unpleasantly surprised" , "Greatly horrify" , "Scandalise" .)