Protestant reformer reported strikes (6)
I believe the answer is:
knocks
'strikes' is the definition.
(knocking is a kind of striking)
I don't understand how the rest of the clue works.
Can you help me to learn more?
(Other definitions for knocks that I've seen before include "Raps on the door" , "criticisms" , "Reversals" , "Strikes with a sharp blow or finds fault with" , "Bangs on door" .)