Strikes, raps (6)
I believe the answer is:
knocks
I believe this is a double definition.
'strikes' is the first definition.
(I know this)
'raps' is the second definition.
(I know this)
(Other definitions for knocks that I've seen before include "You get bad experiences in the school of hard ..." , "Hits" , "Raps, taps" , "Bangs on door" , "criticisms" .)