Dumbfounded that there was no sermon (10)
I believe the answer is:
speechless
'dumbfounded' is the definition.
(I've seen this before)
I cannot understand how the remainder of the clue works.
Can you help me to learn more?
(Other definitions for speechless that I've seen before include "In shock" , "Lost for words" , "Struck dumb" , "Dumbfounded" , "being forced to improvise?" .)