Knocked loudly when drunk (8)
I believe the answer is:
hammered
'drunk' is the definition.
(I've seen this before)
I cannot understand how the rest of the clue works.
Can you help me to learn more?
(Other definitions for hammered that I've seen before include "Forged" , "Thoroughly beaten (colloq.)" , "Hit hard" , "Hit with a hand tool with heavy rigid head and handle" , "Utterly defeated in a contest" .)