He got a crack on the hand (4)
I believe the answer is:
chap
'the hand' is the definition.
(thesaurus)
I can't explain the rest of the clue.
Can you help me to learn more?
(Other definitions for chap that I've seen before include "Bloke, fellow" , "Sore; cheek; man" , "Split in skin" , "(Of skin) become sore" , "Fellow; sore skin area" .)