A man belted at karate (3)
I believe the answer is:
dan
'a man' is the definition.
I cannot understand how the rest of the clue works.
Can you help me to learn more?
(Other definitions for dan that I've seen before include "Grade of judo black belt" , "Dark and damp." , "Expertise level in juso" , "Jacob's fourth son" , "book (abbreviated version)" .)