Pocket violin's chain is rather vulgar (6)
I believe the answer is:
kitsch
'rather vulgar' is the definition.
'kitsch' can be an answer for 'vulgar' (I've seen this before). I'm not certain of the 'rather' bit.
'pocket violin's chain' is the wordplay.
'pocket violin' becomes 'kits' (I can't justify this - if you can you should give a lot more credence to this answer).
'chain' becomes 'ch' (abbreviation for the unit of length).
'kits'+'ch'='KITSCH'
'is' acts as a link.
Can you help me to learn more?
(Other definitions for kitsch that I've seen before include "Tawdry art" , "Item of pretentious bad taste" , "Vulgarly pretentious art" , "tasteless material" , "Garish and in bad taste" .)