Rubbish right outside entrance to oratory (3)
I believe the answer is:
rot
'rubbish' is the definition.
(both can mean nonsense)
'right outside entrance to oratory' is the wordplay.
'right' becomes 'rt' (abbreviation as in Rt Hon- the Right Honourable).
'outside' is an insertion indicator (some letters go outside others).
'entrance to' indicates taking the first letters.
The first letter of 'oratory' is 'o'.
'rt' going around 'o' is 'ROT'.
(Other definitions for rot that I've seen before include "Break down, waste away" , "Decay or disintegrate" , "Decay - nonsense" , "bunk" , "Cobblers" .)