Collection including very loud rubbish (6)
I believe the answer is:
piffle
'rubbish' is the definition.
(thesaurus)
'collection including very loud' is the wordplay.
'collection' becomes 'pile' (pile is a kind of collection**).
'including' is an insertion indicator.
'very loud' becomes 'ff' (musical abbreviation).
'pile' enclosing 'ff' is 'PIFFLE'.
(Other definitions for piffle that I've seen before include "Trivial nonsense" , "Nonsense (colloq.)" , "Informal nonsense, worthless talk" , "Cock" , "rot" .)