Twitch, holding a French garment (5)
I believe the answer is:
tunic
'garment' is the definition.
(historical type of garment)
'twitch holding a french' is the wordplay.
'twitch' becomes 'tic' (tic is a kind of twitch).
'holding' is an insertion indicator.
'a french' becomes 'un' ('a' in French).
'tic' enclosing 'un' is 'TUNIC'.
(Other definitions for tunic that I've seen before include "Loose sleeveless garment" , "Belted coat" , "Loose-fitting shirt or cloak" , "Smock" , "Shift" .)