Horrify a namesake of Revere when speaking (5)
I believe the answer is:
appal
'horrify' is the definition.
(I know that horrify can be written as appal)
I don't understand how the rest of the clue works.
(Other definitions for appal that I've seen before include "Dismay, horrify" , "Outrage" , "Greatly dismay" , "Put at rest (suspicion)" , "expressed dismay" .)