Bechamel? Impudence! (5)
I believe the answer is:
sauce
I believe this clue is a double definition.
'bechamel?' is the first definition.
(bechamel is a kind of sauce)
'impudence' is the second definition.
(I've seen this before)
(Other definitions for sauce that I've seen before include "What's ... for the goose is ... for the gander" , "Cheek (sl.); ketchup" , "Dressing served with food" , "(Semi)liquid flavouring" , "Impertinence; dressing" .)