In vulgar fashion usually (8)
I believe the answer is:
commonly
'usually' is the definition.
(synonyms)
'in vulgar fashion' is the wordplay.
I cannot quite understand how this works, but
'vulgar' could be 'common' (synonyms) and 'common' is present in the answer.
This may be the basis of the clue (or it may be nonsense).
Can you help me to learn more?
(Other definitions for commonly that I've seen before include "Usually, normally" , "Not how the aristocracy behave" , "as a general rule" , "What's very often" , "Usually, ordinarily" .)