Turn out old, disorderly and vulgar (4)
I believe the answer is:
loud
'vulgar' is the definition.
(synonyms)
'turn out old' is the wordplay.
'turn' becomes 'lud' (I am not sure about this - if you are sure you should believe this answer much more).
'out' is an insertion indicator.
'old' becomes 'o' (common abbreviation eg in OE for Old English).
'lud' enclosing 'o' is 'LOUD'.
'disorderly and' acts as a link.
This may not be right. Some or all of it may be part of another bit of the clue.
Can you help me to learn more?
(Other definitions for loud that I've seen before include "booming" , "Forte" , "This speaker is" , "Tasteless; of great volume" , "Noisily showy?" .)