Stumble on last bit of vile rubbish (5)
I believe the answer is:
tripe
'rubbish' is the definition.
('tripe' can be a synonym of 'rubbish')
'stumble on last bit of vile' is the wordplay.
'stumble' becomes 'trip' ('trip' can be a synonym of 'stumble').
'on' says to put letters next to each other.
'last bit of' says to take the final letters.
The last letter of 'vile' is 'e'.
'trip'+'e'='TRIPE'
(Other definitions for tripe that I've seen before include "Cow's stomach lining used as food" , "Edible nonsense?" , "Ox stomach as food - it's nonsense" , "Pants" , "Balderdash" .)