Mix up clothes with French article (6)
I believe the answer is:
garble
'mix up' is the definition.
(I've seen this in another clue)
'clothes with french article' is the wordplay.
'clothes' becomes 'garb' (garb is a kind of clothes).
'with' is a charade indicator (letters next to each other).
'french article' becomes 'le' (definite article in French).
'garb'+'le'='GARBLE'
(Other definitions for garble that I've seen before include "Transmit in distorted version" , "Corrupt" , "Indistinct speech" , "Confuse (a message)" , "Distort text or its meaning" .)