Decide Bristol is full of rubbish (6)
I believe the answer is:
debris
'rubbish' is the definition.
(debris is a kind of rubbish)
'decide bristol is full of' is the wordplay.
'is full of' says the answer is hidden in the clue (inside).
'DEBRIS' can be found hidden inside 'decide bristol'.
(Other definitions for debris that I've seen before include "Fragments of rubbish" , "Scattered rubbish" , "Brides among rubble" , "Scattered wreckage" , "Evidence of destruction" .)