Rude man badly lacking means of defence (7)
I believe the answer is:
unarmed
'lacking means of defence' is the definition.
(having no weapons)
'rude man badly' is the wordplay.
'badly' indicates anagramming the letters.
'rude'+'man'='rudeman'
'rudeman' with letters rearranged gives 'UNARMED'.
(Other definitions for unarmed that I've seen before include "Not able to go into battle" , "Type of combat" , "Like Venus de Milo" , "Having no means of defence" , "Maunder along without weapons" .)