Barbarous and wild leaders of Visigoths ravaged Gaul (6)
I believe the answer is:
vulgar
'barbarous' is the definition.
(thesaurus)
'wild leaders of visigoths ravaged gaul' is the wordplay.
'wild' is an anagram indicator.
'leaders of' says to take the initial letters.
The first letters of 'visigoths ravaged' is 'vr'.
'vr'+'gaul'='vrgaul'
'vrgaul' anagrammed gives 'VULGAR'.
'and' acts as a link.
(Other definitions for vulgar that I've seen before include "Coarse and common" , "Coarse, not in good taste" , "Improper - fractions may be so described" , "Coarse, boorish" , "Indecent" .)