A cloud of smoke we hear to cause dismay (5)

I believe the answer is:

appal

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'dismay' is the definition.
(I know that dismay can be written as appal)

I cannot understand how the remainder of the clue works.

Can you help me to learn more?

(Other definitions for appal that I've seen before include "Cause to be unpleasantly surprised" , "Shock, horrify" , "Scandalise" , "Greatly dismay" , "exhibiting dismay" .)

I've seen this clue in The Globe and Mail.

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