Hop around in rubbish formal attire (3,3)
I believe the answer is:
top hat
'formal attire' is the definition.
(I've seen this before)
'hop around in rubbish' is the wordplay.
'around' is an anagram indicator.
'in' is an insertion indicator.
'rubbish' becomes 'tat' (low-quality items or material).
'hop' with letters rearranged gives 'oph'.
'oph' put into 'tat' is 'TOP-HAT'.
(Other definitions for top hat that I've seen before include "Man's cylindrical headgear" , "Upper-class" , "Item of formal wear" , "Man's headgear with a tall crown" , "Formal head covering" .)