Cuffs a hundred ill-mannered boors (6)
I believe the answer is:
clouts
'cuffs' is the definition.
(I've seen this before)
'a hundred ill-mannered boors' is the wordplay.
'a hundred' becomes 'C' (Roman numerals).
'ill-mannered boors' becomes 'louts' (I've seen this in another clue).
'c'+'louts'='CLOUTS'
(Other definitions for clouts that I've seen before include "Blows, cuffs" , "Informal blows" , "Blows, perhaps around the ears" , "strikes" , "Patches" .)