Cad making rude retort? (6)
I believe the answer is:
rotter
'cad' is the definition.
(I've seen this before)
'rude retort?' is the wordplay.
'rude' indicates an anagram.
'retort' is an anagram of 'ROTTER'.
'making' is the link.
(Other definitions for rotter that I've seen before include "An informal cad, may be decaying" , "One not to be honoured" , "Absolute bounder" , "Mean and unkind person" , "Rogue" .)