The French style of toga is smooth (6)
I believe the answer is:
legato
'is smooth' is the definition.
(musical term)
'the french style of toga' is the wordplay.
'the french' becomes 'le' ('the' in French).
'style of' indicates anagramming the letters (I've seen 'style' mean this (style can mean to shape or design)).
'toga' anagrammed gives 'gato'.
'le'+'gato'='LEGATO'
(Other definitions for legato that I've seen before include "In music, the opposite of staccato" , "Got ale (anag.)" , "Played smoothly" , "Smoothly flowing in style" , "Musically smooth" .)