Advertisement's turned up very loud (4)
I believe the answer is:
puff
'advertisement's' is the definition.
(thesaurus)
'turned up very loud' is the wordplay.
'turned' shows that the letters should be reversed in order.
'very loud' becomes 'ff' (musical abbreviation).
'up' written backwards gives 'pu'.
'pu'+'ff'='PUFF'
(Other definitions for puff that I've seen before include "Light < case" , "Smoke - light pastry" , "Short gust of wind" , "Pull" , "out of which pants come?" .)