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' indicates putting letters inside (some letters go outside others).
'entrance to' says to take the initial letters.
The first letter of 'oratory' is 'o'.
'rt' placed 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" .)