Dressing required impudence (5)
I believe the answer is:
sauce
This clue is a double definition.
'dressing' is the first definition.
(I've seen this in another clue)
'impudence' is the second definition.
(I've seen this in another clue)
'required' acts as a link.
(Other definitions for sauce that I've seen before include "Impertinence (colloq.)" , "sharp language" , "naughtiness" , "Accompaniment to meat ect" , "Liquid on food" .)