On the quiet, new art can be rubbish (5)
I believe the answer is:
trash
'be rubbish' is the definition.
(I've seen this before)
'on the quiet new art' is the wordplay.
'on' is a charade indicator (letters next to each other).
'the quiet' becomes 'sh' ('sh' is used to tell someone to be quiet).
'new' indicates an anagram.
'art' is an anagram of 'tra'.
'sh' after 'tra' is 'TRASH'.
'can' is the link.
(Other definitions for trash that I've seen before include "Rubbish, waste" , "Refuse; wreck" , "Refuse; destroy" , "Anything of poor quality" , "Wreck; rubbish" .)